Category: resistance temperature detector

RTDs

Posted on | by Heatcon Sensors

Advantages of Using RTDs

RTD Probe’s Construction

Wiring Arrangement

Materials of the Wires

The Configuration

Liquid’s Temperature Measurement Using an RTD

Measuring Air & Gas Temperatures Using RTD Sensors

Measuring Surface Temperatures

 

Introducing Resistance-Temperature-Detectors (RTDs)

These happen to be the temperature sensors that tend to consist of a resistor, which alters the resistance value when there are changes in the temperature. These are being used for several years now for measuring temperatures in labs & other industrial processes. These have formed a good reputation for repeatability, accuracy, & stability. Most of the elements of an RTD contain a finely twisted wire that is wound around a glass core or a ceramic. The element is generally very delicate; therefore, it’s usually located in a sheathed protective probe. The RTD element happens to be built of pure materials for withstanding varied temperatures. Material’s resistance changes predictably when there are changes in the temperature; that predicted change is usually utilized for determining the temperatures.

The Origin 

Sir Humphrey Davy saw that metals resistivity showed considerable temperature dependence, and this discovery happened in the same year in which Seebeck discovered thermoelectricity. After 50 years, Sir William Siemens proposed using platinum as the resistance ‘s element.

Advantages of Using RTDs

The resistance temperature detector happens to be the most accurate temperature sensor. In addition to good accuracy, it also offers great stability & excellent repeatability. Such an RTD is even relatively immune to electric noises and are thus suited for temperature measurement in different industrial environments, specifically near generators, motors, & other such high voltage equipment.

RTD Probe’s Construction 

Such probes are the assemblies consisting of one element, one sheath, one lead wire & one terminal/connection. Once the element has been chosen, the wiring & packaging needs are to be decided. Sensors can be connected in many ways & there are unlimited sensors or sensor structures to make the selection.

Wiring Arrangement

For measuring temperatures, the element of the RTD should be joined to a monitoring/control device. Now, as the measurement of the temperature is entirely based upon the resistance of the element, any other resistance that has been added to that circuit (resistance of wires, connections, etc.) can lead to an error in the measurement. Any other wiring than the two-wire configuration allows control/monitoring of the devices to account for unwanted wire resistance & other such resistances inside that circuit. Sensors using a three-wire design happen to be quite common designs utilised for industrial processes as well as monitoring/control applications. The resistance of the wires is considered, provided that all the lead wires are having similar resistance; else errors may occur.

Materials of the Wires

While determining the materials of the lead wire, the correct wires must be selected based on the temperature & environment to which that sensor would be exposed during operation. Temperature is by far the most crucial factor in wire selection, but physical properties like abrasion resistance & water submersion properties could be significant too. The 3 widely popular structures are given as under: 

  • PVC insulated probe provides the temperature range of -40 degrees Celsius to 105 degrees Celsius. It also has nice wear resistance. It is also suitable for water immersion. 
  • PFA insulated RTD probe provides the temperature range of -267 degrees Celsius to 260 degrees Celsius. It also provides supercool wear resistance. It is even perfect for water submersion applications. 
  • Although an RTD probe with fiberglass insulation tends to provide a higher temperature range from -73 to 482 degrees Celsius, its performance is considered less effective when consumed or immersed in water.

The Termination

An RTD probe might be stopped via a connection end, or through a quick disconnect, or by a terminal block or even by an extension wire. There are other finishing styles too. 

The Configuration

As the RTD element, the wire layout & the wire structuring have been chosen, the physical structuring of the sensor must be acknowledged. The configuration of the final sensor largely depends on the type of application needed. Varied sensor configurations are needed for measuring the temperatures of liquids, surfaces, or gas streams.

Widely Popular RTD’s Resistance Materials

  • Platinum (highly accurate & widely popular)
  • Nickel
  • Copper
  • Balco (very rare)
  • Tungsten (quite rare)

RTD standards

There happen to be 2 standards for a platinum RTD. These are 1) the European standard (which is even called IEC standard or the DIN) and 2) the American standard. The European one has been considered the global platinum RTD standard. This particular standard, DIN/IEC 60751 (or only IEC751), needs the RTD for having an electric resistance of 100.00 Ω at 0 degrees Celsius, & also the temperature-coefficient-of-resistance (i.e., the TCR) of 0.00385 Ω/Ω/degree Celsius between 0 degree Celsius & 100 degree Celsius. The amalgamation of temperature coefficient & resistance tolerance tends to determine the resistance & temperature characteristics of such an RTD sensor. The greater is the tolerance of the element, the more the sensor deviates from the general curve & greater will be the variability from 1 sensor to another (which is also called interchangeability). This is significant for those users who require the replacement of sensors & need to curtail any interchangeability errors.

Selecting the Most Ideal RTD 

  • RTD Element: This is RTD’s simplest form. This contains one piece of wire that is wrapped around a glass core or a ceramic. Owing to their small size, such an element is usually utilised where space is quite limited.  
  • RTD Surface Element: This happens to be a special RTD element type. This is made pretty thin, which ensures nice contact for measuring temperatures on a flat surface.  
  • RTD Probe: This happens to be a highly robust RTD form. This contains an RTD element, which has been mounted in a metal tube, which is also called sheath that safeguards the element from the environment.

FAQs

  • Why should one be using an RTD rather than a thermistor sensor or a thermocouple? All types of temperature sensors have specific conditions for which they are ideal. As far as RTDs are concerned, with a wide temperature range up to even 850 degrees Celsius, they could be utilised in most of the industrial processes, even in the high-temperature ones. When an RTD is made with the metals like platinum, these become highly stable, and then they aren’t damaged much by oxidation/corrosion. Other materials including copper, nickel-iron alloy, or just nickel too could be utilised for RTDs. But such materials aren’t used generally as they are having low temperature ability, and they aren’t quite stable also or have repeatable capability as that is there in platinum. So, RTDs provide many benefits, some of which are as follows:
  • Lengthy stability
  • Nice interchangeability
  • Fine accuracy (even better than a thermocouple)
  • Vast temperature range (from around -200 degree Celsius to 850 degrees Celsius)

Liquid’s Temperature Measurement Using an RTD

Sensors that are probe-type are most commonly utilised to measure liquids. These could be quite simple ones having connection heads along with transmitters. Out of these, a widely popular sensor is the quick-disconnect one. It could be utilised as is, with compression fitting for installing flexibly. While doing the measurement of temperature in very harsh environmental conditions like that in plating baths or like in high-pressure systems, these sensors could be covered materials such as PFA Teflon® or contained in a protective housing of thermowell for protecting it against any harsh conditions.

Measuring Air & Gas Temperatures Using RTD Sensors

Measuring air & gas flow is quite a challenge in itself as the rate at which temperature transfers from liquids to sensors tends to be quite slow in the case of liquids. This is why, sensors especially made to be used in air/gas place the sensing element in close proximity to the environment. Such sensors tend to allow the sensing element to be in almost direct contact with the air flow. Such a design is quite popular for measuring temperature of the air in labs, clean rooms, & other such places because the housing design includes elements, which allow air to flow past the element. If such a situation needs some more protection for the sensors, an alternative is to utilise a structure quite like the RTD-860. Such a model has a small-diameter sensor having a mounting flange. The set reacts a little slower to alterations in the air flow, however, it provides better protection for the sensors.

Measuring Surface Temperatures

Measuring surface temperature could possibly be a very intricate thing to do properly & accurately. There’re several styles to make the selection, as per how anyone wishes to mount the sensors, how sensitive the sensor should be to any temperature alterations, and whether or not the installation would be permanent. Some of these are quite speedy & highly accurate responding surface RTDs. 

RTD Glossary

  • RTD: RTD is the abbreviation for resistance-temperature-detector/device. These indicators work on the principle that the electrical resistance of the conductor alters with the temperature.  
  • RTD Element: Part of an RTD sensor that could be built mostly of nickel, platinum, or copper material. 
  • RTD Probe: This happens to be an assembly consisting of an element, a sheath or housing, a wire & a terminal/connection. 
  • Platinum RTDs: Even called Pt RTDs, these are usually the most linear, most stable, most repeatable and highly accurate of all of the other RTDs. 
  • Thin Film RTD: These consist of a thin layer of base metal, which has been embedded in a ceramic substrate & cut for achieving the wished resistance. 
  • Class A RTD: Highest tolerance & accuracy of RTD elements, Class A (IEC-751), alpha = 0.00385 
  • Class B RTD: The most common of the RTD element tolerance & accuracy, Class B (IEC-751), alpha = 0.00385 
  • Aplha .00385 curve: The European curve corresponds to the tolerance of the “0.1% DIN” standard & conforms to the DIN 3760-standard. 
  • Sheath: The casing, a tube with a closed end, secures the element, and protects it against moisture & the medium to be measured. This also gives protection as well as stability to the transition wires from the sensitive element wires. 

Buy an RTD in India – Contact Heatcon 

Heatcon Sensors is a leading name in this domain. If you are looking to buy something of this sort, then you know where to go! Yeah! This is the place to be! Heatcon could be your most appropriate go-to destination for making these purchases. They have brilliant products catering to this domain. Heatcon is a one-stop-shop for all your needs related to temperature sensors. Whichever industry you might be working in, they will have a suitable model for your specific need for sure!

 

 

Choosing between RTD or Thermocouple for an Industrial Application

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When to Use an RTD Sensor?

Advantages of RTD Sensors

Disadvantages of RTD sensors

Thermocouples

When to Use a Thermocouple Sensor?

Advantages of Thermocouples

Disadvantages of Thermocouples

RTD or Thermocouple

 

Temperature measurement is an important aspect of process control and industrial applications. RTD (Resistance Temperature Detectors) and Thermocouples are two types of temperature sensors commonly used in various industries. Both these types of sensors can possibly provide accurate temperature measurements, but the selection between RTD or Thermocouple depends on various factors such as accuracy, temperature range, cost, and application requirements. RTD and Thermocouple sensors work on different principles of operation, which results in differences in their accuracy, response time, and range of temperature measurement.

RTDs

RTD sensors are made of one metal (that is typically platinum/nickel/copper) with a known temperature-resistance relationship. The resistance of the metal changes as temperature changes, and this change in resistance is measured by an external circuit to determine the temperature. RTD sensors provide high accuracy (typically ±0.1°C), and their temperature range can be from -200°C to 850°C, depending on the type of metal used. 

When to Use an RTD Sensor?

RTD sensors are ideal for applications that require high accuracy and stability over a wide range of temperatures. They are commonly used in applications such as food processing, pharmaceuticals, and aerospace industries. RTDs are also suitable for applications where a high degree of repeatability and reliability is required, and where long-term stability is significant.

Advantages of RTD Sensors

  • High accuracy: They provide a high level of accuracy, typically ±0.1°C.
  • Stability: RTDs have excellent long-term stability and repeatability, making them suitable for applications that require high accuracy over long periods of time.
  • Linear response: Such sensors have a linear response to changes in temperature, making them easier to calibrate and more accurate over a wide range of temperatures.
  • Low drift: RTDs have a low drift, meaning that the accuracy of the sensor does not change significantly over time.
  • Wide temperature range: They can measure temperatures from -200°C to 850°C, depending on the type of metal used.

Disadvantages of RTD sensors

  • Cost: RTDs are generally more expensive than thermocouples.
  • Slow response time: These sensors have a slower response time than thermocouples, making them unsuitable for applications that require fast response times.
  • Fragility: Such sensors are more fragile than thermocouples and can be easily damaged if mishandled.

Thermocouples

Unlike RTDs, Thermocouples are made of two different metals (typically chromel & alumel) that produce a voltage when exposed to a temperature difference. The magnitude of the voltage is directly proportional to the temperature difference between the two ends of the thermocouple. Thermocouples are less accurate than RTD sensors, with an accuracy typically ranging from ±1 to ±10°C. However, they have a wider temperature range of -200°C to 2300°C.

When to Use a Thermocouple Sensor?

Thermocouples are suitable for applications that require a wide range of temperature measurement and fast response times. They are commonly used in applications such as HVAC systems, industrial furnaces, and laboratory experiments. Thermocouples are also suitable for applications where the sensors need to be small and where a low cost is essential.

Advantages of Thermocouples

  • Wide temperature range: They can measure temperatures from -200°C to 2300°C, making them suitable for a wide range of applications.
  • Fast response time: Thermocouples have a fast response time, making them suitable for applications that require fast temperature measurement.
  • Cost: They are generally less expensive than RTD sensors.
  • Durability: These are more durable than RTD sensors and can withstand rough handling and harsh environments.

Disadvantages of Thermocouples

  • Lower accuracy: The accuracy of thermocouples is generally lower than that of RTDs, typically ranging from ±1 to ±10°C, depending on the type of thermocouple.
  • Non-linearity: The output voltage of thermocouples is not linearly proportional to temperature, which can make calibration and accurate measurement difficult, especially at lower temperatures.
  • Drift: The output of thermocouples can drift over time, which can affect their accuracy and require frequent recalibration.
  • Limited lifespan: The lifespan of thermocouples is generally shorter than that of RTDs due to their construction and the effects of aging.
  • Signal interference: The output of thermocouples can be affected by electromagnetic interference from nearby electrical equipment or wiring, which can affect the accuracy of measurements.

RTD or Thermocouple

While selecting between RTD or Thermocouple during the lookout for an appropriate temperature sensor depends on various factors such as the accuracy required, temperature range, response time, and cost. Both RTDs and thermocouples have their advantages and disadvantages, and it is important to consider these factors when selecting the appropriate sensor for a particular application. 

Come to Heatcon for Procuring the Best Range of Such Products 

If you are looking for an RTD or Thermocouple, Heatcon can be the best place for you to make such a selection for the appropriate sensor for a specific industrial application.

 

 

Factors That Direct the Cost of Temperature Sensors

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Cost of Temperature Sensors

Factors Directing the Cost of Temperature Sensors

Heatcon Can be Your Go-To Destination for Procuring the Most Ideal Temperature Sensor(s)

Temperature Sensors

Temperature sensors are electronic devices that measure and monitor the temperature of various objects and environments. They play a vital role in a variety of industries, including HVAC, food processing, automotive, healthcare, and aerospace. 

Cost of Temperature Sensors 

Buyers’ biggest concern seems to be the price front, as most of them assume that all types of temperature sensors cost the same, which is not the case! This is because all industrial applications of temperature sensors are not the same, so all temperature sensors cannot be created as equal, therefore their prices tend to vary. The prices of RTDs & thermocouples are largely determined by different factors, like the applications for which they might be used for as well as the temperatures at which they will be operating. For example, the temperature sensors which measure the air temperature in a particular room would vary from the one that is utilised for measuring 1400 degree Celsius in an industrial heat treatment process. It all means that getting the right tool for the job is important!

Factors Directing the Cost of Temperature Sensors

The cost of temperature sensors can vary greatly, depending on several factors, as explained below:

  • Market Application: One of the most significant factors driving the cost of temperature sensors is the market application. Sensors used in high-end applications such as aerospace and medical equipment have higher accuracy, precision, and reliability requirements, which drives up the cost. Sensors used in less critical applications, such as household appliances or automotive engines, may have lower accuracy and precision requirements, resulting in lowering the costs.
  • Temperature Measuring Range: Temperature sensors are designed to measure temperatures within specific ranges. The wider the temperature measurement range, the more complex the sensor construction needs to be, which increases the cost. For example, a sensor designed to measure temperatures from -40°C to 125°C will be more expensive than a sensor that measures temperatures from 0°C to 50°C.
  • Hazardous Locations: Sensors used in hazardous locations, such as petrochemical plants, must meet specific safety requirements. They need to be explosion-proof, intrinsically safe, or have other protective measures to prevent accidents. This additional safety equipment adds to the overall cost of the sensor.
  • Construction of the Sensors: The cost of temperature sensors also depends on the sensor’s construction. Some sensors are designed to be small & lightweight, while others are intended to be durable and withstand harsh environments. The type of materials used to construct the sensor, such as stainless steel or plastics, can also affect the cost.
  • Options & Accessories: The cost of temperature sensors can vary based on the additional options and accessories that come with them. For example, sensors with wireless connectivity, calibration certificates, or custom-designed probe configurations can be more expensive than basic models.

Heatcon Can be Your Go-To Destination for Procuring the Most Ideal Temperature Sensor(s)

Overall, the cost of temperature sensors depends on several factors, including market applications, temperature measurement range, hazardous location approvals, sensor construction, and options and accessories. It is always essential to consider these factors when selecting a temperature sensor to ensure you get the most suitable sensor for your application while also staying within your budget. You can reach out to Heatcon Sensors for procuring the best products in this regard.

 

 

Let Us Look at the Detail about Pt100 Probe

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What is a Pt100 probe?

Termination

Lead Wire

Element

Sheath

Temperature Rating

Types & Specifications

What is a Pt100 probe?

If you have been wondering what a Pt100 probe is, then you are not alone. The Pt100 probe is basically the assembly that consists of the RTD’s element, one sheath, one lead wire & also one terminal or one connection. The Pt100 happens to be a temperature sensor, which contains one resistor, which tends to change the resistance value when there are changes in the temperature. Such a type of probe is commonly used in temperature measurement and control, and it is important to understand how it works in order to get accurate readings. The Pt100 probe is used in a variety of applications including temperature measurement, process control, and thermal management. The Pt100 probe has a wide range of temperature ratings and can be used in both Cryogenic and High Temperature applications. The Pt100 probe can be terminated with a variety of lead wires and sheaths.

 

Termination

A Pt100 probe could be terminated inside a connection head, in the fast disconnect, in the terminal-block or also in the extension wire. The standard terminations are described on the product-related pages. Other styles of termination are available by special order. 

Lead Wire

Pt100 probes also have lead wires, which are used to connect the probe to a measuring device. The lead wires are usually made of copper or another conductive material. Lead styles & RTD cables of extension tend to be provided in 1 of the 4 configurations. Style two is the standard. Ensure selecting a configuration, which matches the instrumentation. Some probes are also available with different types of lead wires, depending on the application.

Element

A Pt100 probe consists of a Pt100 element, which is a resistive material that changes resistance with temperature. 

The standard RTD probe has been built from a 100 ohm European platinum curved element (á = 0.00385). 

Sheath

The element is encased in a sheath, which is typically made of stainless steel. The sheath protects the element from damage and also helps to ensure accurate readings. The sheath, the tube with a closed end, secures the element and also protects it against any moisture content & other environment for measurement. The sheath too gives protection as well as stability for the lead wires of transition of the sensitive element wires. The standard sheaths are 3 mm (1/8″) & 6 mm (1/4″) O.D. 304 tubes made of stainless steel material. 

Temperature Rating

Pt100 probes are available in a variety of temperature ratings, which determine the range of temperatures that the probe can accurately measure. “PR” Style of the RTD’s probe assemblies have been rated to be used in temperatures largely up to even 600 degree Celsius (1110 degree Fahrenheit). The style sensor of “PRTF” has been rated up to the range of 260 degree Celsius or 500 degree Celsius as per the design. The limitations for the temperatures might be placed upon the styles of termination because of the insulation used in the wire. The rating of maximum temperature has been made available by special order, and it can be 750 degree Celsius (1380 degree Fahrenheit). 

Heatcon Sensors

If you have been looking for accurate temperature readings, a Pt100 probe is a great option. This type of probe consists of a thin wire that is wrapped around a metal rod. The wire is then connected to a monitoring device. Pt100 probes are often used in industrial settings, as they are able to withstand high temperatures. They are also available in different sizes and with different lead wire and sheath options, so you can choose the best option for your needs. Keep in mind that the element and temperature rating of the Pt100 probe will affect its accuracy. When using a Pt100 probe, it is important to choose the right termination for the lead wires. This will ensure that the readings are accurate and that the probe is properly connected to the measuring device. For procuring the right type of products, you can come to Heatcon!

Describing the Equipments for Calibration Systems

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Standard PRT

Secondary SPRTs

Master Thermocouples

Dry Block Calibrator

Coefficient of Uncertainty

The equipment that is needed for performing temperature sensors’ thermal calibration largely depends upon the desirable accuracy as well as easiness of usage. The larger is the precision needed, the more demanding is the procedure as well as the costs. The equipments for Calibration Systems is usually divided into 1 of the 3 groups.

  1. The general purpose system used to test temperature sensors in industrial plants generally provides an accuracy of 1.0 degree Celsius to 0.1 degree Celsius making use of the comparison techniques. 
  2. A secondary standard system used for high-quality comparisons as well as fixed-point measurement typically provides an accuracy of 0.1 degree Celsius and 0.01 degree Celsius. 
  3. The primary standardization system makes use of the highly advanced & precise equipment for achieving accuracy better than 0.001 degree Celsius. 

Typical equipments utilized for comparison calibration include the following: 

  • A standard PRT or the secondary PRT
  • Multiple temperature baths
  • System for data acquisition

  • Temperature Sensors

For low temperature calibration, Platinum resistance detectors are utilized as SPRT & RTD forms, which are quite stable as well as highly accurate. A noble-metal thermocouple, such as an R, S type, is utilized for high temperature calibration. Such sensors should have accuracy & repeatability. 

Standard PRT

SPRT or Standard-Platinum-Resistance-Thermometer happens to be a highly accurate standard that is currently available, but it is also quite an expensive one, & other such standards are the better acceptable alternatives as per the temperature ranges covered, desired accuracies, capability , or calibration lab preferences. 

Secondary SPRTs

These are much more usable & deal with less processing interferences. It is cheaper than SPRT. 

Master Thermocouples

These are utilized as reference sensors in the comparison calibration processes. These are placed together with the calibrated sensor in quite a stable temperature zone, and their values ​​are compared & errors are calculated. 

  • Temperature Reading Methods

These devices measure the power of sensors; they should be having higher resolution as well as fine accuracy. 

  • Secondary Temperature Sources

Dry Block Calibrator

This provides a highly convenient portable device for monitoring industrial sensors & typically achieves relatively fast heating and cooling. 

Stirred Liquid Bath

Such a bath provides an excellent thermal environment for probe immersion because there’s no air gap between probe & medium. 

Ice Baths

Such a bath consists of a mixture of melting shaved ice & water. 

Negative Baths

Negative Bath & Ice Bath are primarily utilized for RTD calibration, providing negative temperature for the application of lower temperature calibration. 

Fluidized Calibration Bath

Such a bath is a unique way to obtain precisely controlled temperatures. 

Coefficient of Uncertainty 

In the past, test device error or inaccuracy was usually a concern when the test device was used as a reference. The concept of uncertainty is now often used in the calibration of precision instruments, where high precision is required in the measurement. This concept is viewed based on several significant parameters. Today, calibration labs must calculate & add total/expanded uncertainty to all measurements while calibrating test instruments. This should be noted that “error” isn’t “uncertainty”.

Heatcon Sensors 

There’s a potent company providing high-quality products in this domain and that is Heatcon Sensors!

About the Inspection and Testing of the Sensors

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Heatcon Sensors

Various tests are performed to ensure the quality of the sensor: 

  • Type Test: Such testing that is usually performed to demonstrate compliance with the specification is called a type test. The purpose of such a test is to show the general characteristics & design of a particular sensor sample. 
  • Routine Test: Such a test that is performed on each sensor according to the sampling plan is known as the routine test.

 

Important quality assurance tests are as follows: 

  • Inspection of Appearance & Construction: Visual inspection ensures conformance of thermocouple assembly to specification, drawing & materials. The finish of seams, joints, welds, name-plates/tagging-plates and other parts are visually inspected for any defects, dirt and roughness on the surface. If needed, welds and fittings can be subjected to a dye-penetration-test, hydrostatic pressure testing and even X-ray inspection. 
  • Dimensional Checks: Unless otherwise stated, dimensional checks are made according to the tables using a straight gauge, Vernier Caliper, and even gauges. 
  • Insulation Resistance Test: Such testing is usually performed with a super megohmmeter by applying a steep temperature gradient to the sensor assembly that has been immersed in a boiling water-bath for accelerating the condensation of residual moisture in the assembly. Such testing allows a very precise measurement of the assembly’s insulation resistance between the sheath and the terminal. 
  • Emf Calibration Tests: Such a test could be performed by two ways, one with the standard method with RTD or standard thermocouple, and second option is by the absolute method using fixed point standards in each unit or set at 3 points of the preset temperature as per the sensor type. 
  • Pressure Tests (Only for Elements That Are Sealed): The element would be tested in a hydraulic testing chamber where ice & water are in equilibrium, and they are electrically connected to a suitable indicator. The fluid pressure in the chamber should be increased to 35 kgf/cm, and then maintained for 15 mins. The element’s resistance or EMF must not deviate considerably enough from the equilibrium temperature that corresponds to the applied pressure, and when the element is later removed from that chamber, it must pass the accuracy test as well as the insulation resistance testing. 
  • Thermocouple Type Identification Test & Polarity Test: Either immersing the thermocouple in the boiling water bath above or applying hot air/flame heat to the hot-end/cold-end of the bead thermocouple to produce an EMF that allows a certain type of thermocouple to be plotted on Temperature vs. EMF-table. A DC circuit tester that is high in resolution tends to be utilized for identifying the thermocouple type & the polarity of the thermocouple’s terminal & its leg.
  • Others: Loop Resistance tests, pressure tests, X-ray tests, vibration tests, voltage withstand tests, helium leak tests, etc. could even be done if requested.

Heatcon Sensors

Heatcon happens to be that ultimate stop where you can find the best range of products in this regard.

Gain Information about Thermowell Special Coating

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Thermowell Special Coating

Variety of Thermowell Special Coatings

Tests on Thermowell 

Thermowell Material Selection

 

Most industrial facilities rely on some form of temperature measurement in order to monitor and control processes. One of the most critical aspects of temperature measurement is the thermowell. A thermowell is a protective sleeve that houses the temperature sensor. It acts as a barrier between the process and the sensor, allowing the sensor to be removed or replaced without disrupting the process. The thermowell is basically the component that is used to protect sensors from high temperatures. In order to prevent damage to the sensor, a thermowell is often used. This tube-like component is inserted into the process stream. The sensor is placed inside the thermowell. The thermowell protects the sensor from the high temperatures of the process stream. The thermowell also allows the sensor to be removed from the process stream without interrupting the process. Thermowells are often subjected to harsh conditions, which can lead to corrosion and wear. In order to protect the thermowell and extend its lifespan, many facilities specify a special coating for their thermowells.

Thermowell Special Coating

Thermowells are often coated with a special coating to protect the sensor from the high temperatures of the process stream. The coating also allows the sensor to be removed from the process stream without interrupting the process. The coating is applied to the thermowell before the sensor is placed inside the thermowell. The coating is applied to the outside & inside of the thermowell, to the sensor, lead wires, electrical connections, solder joints, terminals, housing, base, cover, mounting bracket, support bracket, gasket, seals, o-rings, washers, screws, and nuts & bolts.

Variety of Thermowell Special Coatings

There are a variety of special coatings that can be applied to thermowells, depending on the specific needs of the application. Some common special coatings include:

  • Teflon
  • Tungsten
  • Boron Nitride
  • Zirconia 
  • Alumina
  • Stellite 

 

The type of special coating that is applied to a thermowell will depend on the specific needs of the application. In many cases, a combination of coatings may be used in order to achieve the desired results. If you are specifying a thermowell for a temperature measurement application, be sure to discuss your coating requirements with your supplier. They will be able to recommend the best coating for your particular application.

Tests on Thermowell 

Some Thermowell tests include the following:

  • Radiography
  • Material tests
  • Dimensional tests
  • Dye penetration tests
  • Hydrostatic pressure tests

Thermowell Material Selection 

The choice of material is the most significant aspect in the service life of a thermowell. Selection of the thermowell is entirely based on the application temperature & process environment.

  • Connection: This happens to be the installation factor
  • Insertion Length: This happens to be the accuracy factor
  • Bore Size: This happens to be the interchangeability factor
  • Tapered/Straight Well: This happens to be the factor for velocity rating 

PTC 19.3 Thermowell Standardization 

ASME (American-Society-of-Mechanical-Engineers) PTC (Performance-Test-Codes) have been made use of for determining the performances of particular, mechanical equipment that tend to be constructed for meeting some required criteria for performance as well as operability. 

Heatcon Sensors

Thermowell Special Coating is a type of coating that is applied to thermowells in order to protect them from the environment and extend their life. There are many different types of thermowell special coatings available, each with its own set of benefits. Choosing the right coating for your thermowell is important in order to get the most out of it. Contact Heatcon for the best range of products in this domain.

 

 

Get Complete Knowledge on Thermowell Tip Profile

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Basic Thermowell Structure – Shank Construction

Flange Face Types

Thermowell Welding

WPS & PQR

 

Thermowell Tip Profile

  • Tapered: The outside diameter progressively reduces along the length of the immersion. This is utilized for various high-speed applications. 
  • Flat Tip: One end of this is having a flattened surface. This one is utilized for low-pressure applications or in places where the flow characteristics that are around the body aren’t that significant. 
  • Domed Tip: This type of protective cover has a hemispherical tip at the thermowell at one of the ends. This one is utilized in various high-pressure applications or in places where the flow characteristics, which are around it, are quite significant. 
  • Spherical Tip: For this, a special drill with 118ºC tip angle is utilized for thermowell’s production. The end is spherical i.e. in the shape of a ball, for achieving wall thickness as uniform as possible. 

Basic Thermowell Structure – Shank Construction

  • Q-Dimension: This happens to be the shank’s thickest segment on the hotter side of flange or process connection. This depends on the size of the bore & that of the process connection. 
  • Bore size: This is Thermowell’s inner diameter. This can also be referred to as the diameter of the cylindrical cavity inside the thermowell or protective tube. The standardized drilling dimensions are 6.5mm and 8.5mm. 
  • Immersion U-Length: Thermowell’s length or that of the protecting tube, which is under the flange, the mounting threads, the bushing, etcetera; extending into the area of the process. This length, ‘U,’ is actually measured from the process connection bottom to that of the Thermowell’s tip. 
  • Lagging Extension T-Length: Additionally to the standardized head lengths, the trailing extension length is required to allow access to the end of the trailing extension and allow the probe to reach through insulation/walls. 
  • Inside Mounting Thread: Thermowell’s inside thread shields to secure the junction temperature device & nipple extension for the assembly of a Thermowell. 

Flange Face Types

  • Raised-Face or RF: This is the most commonly used flange type, and this one can be easily identified. This is called an RF or the raised surface as the sealing surfaces are raised above the surface of the bolt circle. 
  • Ring-Type Joint or RTJ: Its flanges have grooves, which are cut into the surface that seal with steel rings. 
  • Flat Face or FF: This one has a sealing surface that is in the similar plane as the surface of the bolt circle. 

Thermowell Welding 

Welding is actually the process in which 2 metals are joined by heating them to a suitable temperature. This can be made with or without pressure, and with or without any filling. The 2 main types are as under:

  • Full Penetration – This particular type of weld provides a fully-welded interface between 2 parts & is usually the sturdiest joint. 
  • Partial Penetration – This particular type of weld consists of an interface that is partially welded with a filler metal placed on the surface of the 2 metals.

WPS & PQR 

WPS stands for Welding-Procedure-Specification. It is actually a document, which tends to describe the process of welding and how it should be done in production. These are advisable for all sorts of welding operations as well as the many application codes & standards tend to make them kind of mandatory.  WPQR or PQR is shortened to Procedure-Qualification-Record. This is something that supports the WPS. This is actually a test-weld that has been made & tested (quite rigorously) for ensuring a good weld with the procedure.

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Information about Industrial RTD Probes

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Probe Assemblies

Flexible Resistance Thermometers

Resistance Thermometer for Special Purposes

Applications of Resistance Thermometers

Advantages of Platinum Resistance Thermometers

Limitations of Platinum Resistance Thermometers

 

Industrial RTD Probes

Encapsulated probe is basically a resistance thermometer’s standard configuration usually for industrial process control as well as protection of the machinery. Most of such probe cases tend to be of stainless steel or Inconel for withstanding extreme temperature, though other material provides better benefits in the mid-range. Standard diameter of the probe ranges from 0.125. to 0.250. Small sized probes tend to react faster when they are inserted directly, however large sized probes fit much tightly into the standard protective covers. The length-range of a probe tends to vary between some inches to even 10 feet or even more than that. 

Probe Assemblies

A wide range of mounting parts as well as accessories tends to assist in the installation of sensors. The choice is largely based upon the nature of the detected carrier and the cost needs. Direct probe immersion needs a threaded connection that can be fitted well or welded to the probe. 

Flexible Resistance Thermometers

The encased probe is not very suitable for detecting flat surfaces. Unlike the junctions in thermocouples that could be soldered straight to metal surfaces, RTDs provide some mass; & heat loss to the surrounding air, which can tend to affect the reading. Small-sized flattened elements like thin films could also be mounted to the surfaces, but sensitive elements as well as wire connections tend to make the process installation much more difficult. 

Resistance Thermometer for Special Purposes

A resistance thermometer tends to adapt easily to most models of process control & thermal equipment. The users can specify axial lead enclosures for the mounting of the circuit boards, flat packages in order to clamp to the surface(s), mini enclosures for embedment in metal blocks, and any fittings & sheaths that can all be produced by a machine shop. Additionally, windings of the wires could possibly be configured for detecting larger regions. 

Applications of Resistance Thermometers

In general, resistance thermometer offers the maximum number of benefits over other types of thermometers in the following situations: 

  • High standardization is desirable 
  • Sensing of area, instead of point, betters control 
  • Accuracy should be extending over a vast range of temperature
  • Accuracy & stability being the most important application goals  

Advantages of Platinum Resistance Thermometers

  • Lesser drift 
  • Higher accuracy 
  • Wide range of applications 
  • Suitability for specific and precise applications  

Limitations of Platinum Resistance Thermometers

  • A resistance thermometer in industrial application is rarely used above 600 degree Celsius. At a temperature above 660 degree Celsius, it tends to become highly difficult to avoid contamination of the platinum with the metal shell of the thermometer. Therefore, standard lab thermometers replace the metal sheath with a glass construction. At a very low temp, say somewhere around -270 degree Celsius (i.e. 3K) or even lower than this, the reason being quite a lesser no. of photons, the resistance is principally measured by the impurities as well as boundary diffusion; and therefore, essentially temperature independent. Resultantly, RTD sensitivity is largely zero, so it is not quite useful. 
  • Compared to a thermistor, platinum resistance thermometer is less sensitive to minute temperature alterations & has a much slower reaction time. But a thermistor has a much smaller range of temperature as well as stability.

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Potential Sources of Error in RTD

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Sources of Error in RTD

RTD’s i.e. the Resistance-thermometer-systems are prone to 3 major sorts of errors:  one is the tolerances built into the thermometers inherently, second is with the gradients between the thermometer & the measuring medium, and third type of errors in the path between the sensor & the display/control device. Some error sources are purely electronic; while others can be due to the mechanical designing of the thermometers. 

  • Conformity or Interchangeability: Interchangeability or conformity defines the amount of resistance by which the thermometer is allowed deviation from the standard curve.
  • Sensitivity: The change in resistance per degree temperature change is actually the function of the base resistance as well as TCR (which is the Temperature-Coefficient-of-Resistance). 
  • Insulation Resistance: If the sensing element & the leads are not insulated fully from the housing, a bypass effect happens, wherein, the housing tends to become a parallel resistance that tends to lower the apparent values. 
  • Self-Heating: The resistance thermometers are the passive resistance sensors; they need a measured current for producing beneficial signals. As this particular measuring-current tends to heat up the cell wire above the actual ambient temperature, errors are bound to occur if excess heat is not being dissipated. 
  • Time Constant: The time constant is actually the indicator of the sensitivity or responsiveness of the resistance thermometers to any temperature changes. The rate of these responses is dependent over the thermometer’s mass as well as the rate at which heat is being transferred from the outermost surface towards that of the sensing element. A faster time constant decreases the chances of errors in the system subject to quick changes in the temperature. 
  • Repeatability: The amount of agreement between 2 consecutive readings of any thermometer happens to be its repeatability. Loss of this repeatability may lead to temporary or permanent changes happening in the element’s resistance characteristics & they can eventually lead to exposing the thermometer to temperatures which are at some specified range endpoints or above them. 
  • Stability: Being stable is a long deviation of the readings of the thermometer. A normal specification limits such deviations to only 0.1 degree Celsius per year in nominal mode. Usual services that stay well within the temperature range tend to result in very less drift. Drift is actually the consequence of the element’s material; platinum happens to be the most stable one; encapsulating those materials that can contaminate the element; as well as the mechanical stress which is there on the element due to the expansion of coils or some other supporting structure. 
  • Shock & Vibration: Mechanical shock as well as vibration tend to alter the reading of any such thermometer or can also lead to total failure. In reality, stability as well as durability is somewhat unique. Designed for maximum stability, the lab thermometers contain unsupported elements that are too sensitive for use in industrial applications. The elements of most such industrial RTDs are supported completely by the bobbin or some other packaging material, so that they can withstand even the most extreme environments quite well. 
  • Packaging & Heat Transfer: Sheaths & other such structures neighboring resistance elements must be maximizing the transfer of heat from any detected environment, and must be minimizing the transfer of heat from any environment that can change the reading, & thus provide the elements with the required protection.

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Let’s Delve Deeper into the Concept of Mineral Insulated RTD

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Metal Sheathed RTD

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Mineral Insulated RTD

Mineral-insulated (M.I.) resistance thermometers are usually equipped with platinum measuring resistors (i.e. Pt100 Ω) according to DIN IEC 751. The inner conductors (Cu) have been embedded in densely packed inert mineral powder (i.e. MgO) which measures that the resistor has been connected to the internal conductors; and it is also surrounded & embedded in a metal shell, thus forming an assembly that is hermetically-sealed. Constantan & nickel inner conductor(s) are also sometimes utilized. Cover is a useful protection in most of the circumstances. These are used in places where a quick response, lesser space and/or vibration resistance is required. These could be equipped with a fixed cable or a special connector that allows quick installation or replacement. Such Mineral Insulated RTD temperature sensors usually have flexible, thin-walled mineral-insulated stainless steel cables with low-resistance copper wires that have been braided in compressed heat-resistant magnesium oxide. The temp-probe is well-connected to internal wiring and placed in a stainless steel case. Thermowell & mineral-insulated cable have been welded together. Proper heat transfer between the housing & the temp-probe enables a short response time & high measurement accuracy. Anti-vibration (vibration-resistant) design ensures long service life. Temperature measurement of hard-to-reach measuring points is possible; thanks to a flexible cable with mineral insulation. The smallest bending radius is five times the outside diameter.

Metal Sheathed RTD

  • Consists of thin-walled & flexible stainless steel mineral-insulated cable. 
  • The cable consists of low-resistance inner wires, which are made from compressed refractory magnesium oxide. 
  • Temperature sensor being well-connected to internal wires & installed in the protective tube. 
  • The protective tube & sheath cable have been hermetically connected. 
  • Proper heat transfer in the protective tube & the temperature sensor enables quick response time & high measurement accuracy. 
  • Flexible sensor tubes enable measuring of temperature in hard-to-reach places. 
  • These are being utilized in heavy measuring applications with high vibration and in all measuring positions where flexibility & exchange ease have been required. 
  • Applications can be seen in power plants, chemical plants, engines, and mechanical engineering & construction facilities along with some usual industrial applications.

About Heatcon Sensors 

With more than thirty years of experience in manufacturing temperature sensors & heaters, Heatcon provides high-quality, precision and an unsurpassed commitment to customer support. Ours is a world-renowned firm with vast experience of our employees, who are provided with continuous training in all areas of the businesses so that they can continue providing excellent service as well as product support to all our esteemed clients.

 

 

Gaining Knowledge about RTD Wire Configuration

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Two Wire RTD

Three Wire RTD

Four Wire RTD

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RTD Wire Configuration

RTD is available in 3 different types of wire configurations. The choice of such lead wire configuration is entirely dependent on the expected accuracy as well as on the instrumentation that is being utilized for measurement purpose.

Two Wire RTD

Of the 2 wires, the RTD has the simplest circuit configuration. 1 of the wires is attached to each of the sides of the element. The measurement can be made with any device that has been equipped for measuring resistance, which includes the basic VOMs (i.e. the volt-ohmmeters). This is the least accurate method of measuring temperature because the resistance of the lead wire is in serial conjugation with the sensing element. The lead wire is at a temperature different from the sensing element, and is also having varied resistance & temperature characteristics. More the length of the wire, the bigger is its effect over the measurement.

Three Wire RTD

Three-wire RTDs happen to be the most popular configurations for use in industrial applications. Three wires can be used to minimize the effect of wire resistance. Making use of this way, the 2 wires leading to the sensor are on adjacent branches. Each leg of the bridge has a lead resistor, so the impedance cancels as long as the two lead resistors are exactly the same. This type of configuration allows up to 600 meters of cable. When utilized in the correct fashion, the three-wire configuration removes any series resistance, which allows accurate measurement of the sensor element. Two wires are connected to one side of the sensor element and one wire to the other side. The resistance of L1 & L3 must be very close as much as possible; which will cause the resistance of the wire to decrease. The color code for a three-wire RTD is 2 red and 1 white.

Four Wire RTD

Four-wire RTDs are the most accurate ways of RTD measurement. They are mostly used in labs & are rarely seen in any kind of industrial applications. The 4-wire resistance thermometer configuration augments the accuracy as well as the reliability of the measured resistance: the resistance error is zero due to the resistance of the lead wire. Four-wire RTD circuits eliminate the effects of mismatched resistors in the wires. Constant current passes through L1 & L4, L2 & L3 measure the voltage drop across the RTD elements. Four-wire RTDs are mostly color-coded as 2 red and 2 white wires. 

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Let’s Discuss the Different Types of RTDs

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Other RTDs Types

Standards of RTD

RTD Construction

 

Types of RTDs

The Platinum-RTDs are generally offered in 2 different categories; 1st is the ‘Class A’ & the other is ‘Class B.’ 

  • Class A: This one is presumed to be high in accuracy, and also, this one has ±0.06 ohms ice-point-tolerance. 
  • Class B: This one is known to have standard accuracy, and also, this one has ±0.12 ohm ice-point-tolerance. This type B is used popularly in most of the industry verticals.

Other RTDs Types

  • PRT or the Platinum-Resistance-Temperature Sensor: These provide awesome accuracy over a vast range of temperature (ranging from -200°C to even up to 850°C). 
  • Other options for resistance value: The RTD elements are even provided with resistances of 200 Ω, 500 Ω and 1000 Ω at zero degrees Celsius. These RTD types are commonly called PT200, PT 500 & PT 1000 respectively. 
  • SPRT or the Standard-Platinum-RTD: ITS-90 (1990 International-Temperature-Scale that is utilized as a global practical scale for temperatures in the laboratories of national metrology such as NIST & NPL etc.) consists of several fixed reference points as well as various interpolation devices, which are made use of for determining the scale amongst the points.

Standards of RTD

Platinum RTDs have basically 2 standards

  1. European standard (this is also called the DIN/IEC standard) 
  2. American standard

RTD Construction

RTD elements almost permanently need insulated conductors. At a temperature below about 250 degree Celsius, the PVC, silicon rubber or the PTFE-insulator are majorly made use of. Fiberglass or ceramic is used over it. The measuring point, & largely most wires, needs a housing/sleeve protection, which is usually made from metal alloys, which are chemically inert to this process that is under monitoring. 

  • Platinum Thin Film: RTD’s thin film style is perhaps the most known model due to its rugged design & less price. For making a thin film element, a small ceramic chip is covered with a very thin (0.0001″) platinum film & then a resistive path is cut or chemically etched into the platinum film. After that, the element is covered with quite a thin glass layer for protecting it from harmful chemicals as well as gases. 
  • Internal Coil Wire Wound: This type is usually made of platinum wire. A very small platinum wire (0.02 mm) is twisted & after that slipped into a small 2-hole ceramic insulator. After that, big extension wires are welded to the platinum wire ends & cemented in. Some of the manufacturers fill the insulating holes with ceramic powder after the coils are installed. This prevents the coils from moving & shorting against one another. The one end, which is right opposite the extension wires, is also coated with ceramic cement. 
  • External Wound Element: An external wound element of RTD is formed by winding the sensor element wire around the central mandrill that is generally formed from ceramic. After that, this coil or winding is covered with glass/other material for insulating so as to protect & secure the winding. These wires are then welded to the extension cords & after that secured to the frame with ceramic epoxy/cement.

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All You Need to Know about the RTD Sensor

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RTD

RTD Materials

Temperature Rating

 

Introduction 

Sir Williams Siemens, in the year 1871, was probably the 1st to introduce temperature measurement using the resistance/temperature characteristics of various materials and largely laid the foundation for modern resistance thermometry. The resistance of the material is given by the given formula:

R = (ρ × L)/A

In this:

  • R is for Resistance (measured in ohms)
  • ρ stands for Resistivity (measured in ohm/cm)
  • L is for Length (measured in cm)
  • A stands for Cross-sectional area (measured in cm )

History 

Sir William Siemens proposed using platinum metal as an element inside the resistance thermometers. Platinum is particularly suitable for this very purpose because it has the ability to withstand high-temperature while still maintaining great stability. As a precious noble metal, it has very limited susceptibility to any sort of contamination. The classic RTD design i.e. the design of the resistance-temperature-detector with platinum was given by C.H. Meyers in the year 1932. Another lab standard replaced Meyers’ design. This was the birdcage element, which was proposed by Evans & Burns. Resistance changes with time & temperature due to voltages were minimized, and the birdcage became the ultimate lab standard. However, due to the unsupported construction & subsequent susceptibility to any kind of vibration, this configuration proved to be very delicate for industrial environments. There were then the partially supported versions of RTD that offered a compromise between the birdcage’s approach & the sealed helix. One of these approaches makes use of a platinum helix threaded via a ceramic cylinder & secured with a glass alloy. These devices maintain great stability in moderate vibration applications.

RTD

RTD resistance & temperature characteristics are stable, repeatable, and have an almost linear positive temperature coefficient from 200°C-800°C. Such characteristics make an RTD the de facto industry standard. The temperature is calculated by measuring the resistance & then utilizing the RTD.s .R vs T. characteristics for extrapolating the temperature. Superior sensitivity & superior stability of such devices compared to thermocouples provide them significant pluses in the low & medium temperatures. Additionally, resistive devices generally simplify control & readout electronics. Resistance thermometers might be known as the RTD or the PRT (i.e. the platinum-resistance-thermometer), or the SPRT (i.e. the standard-platinum-resistance-thermometer). Chemical stability as well as availability in the purest form, and greatly reproducible electrical characteristics has made platinum the chosen metal for RTD, made from either the IEC/DIN grade platinum or from the reference-grade one. The difference is in metal’s purity. The IEC/DIN standard one is pure platinum, which is contaminated intentionally with some other platinum.

RTD Materials

Some common RTD materials are copper, platinum, nickel, Balco (which is basically an alloy made of seventy percent of nickel & thirty percent of iron). The benefit of all these metals is that they could be produced in very high purity and are therefore available with very reproducible temperature/resistance properties. Such metals can even be drawn into the fine diameter wires needed in resistance thermometry.

Temperature Rating

The max temp rating of an RTD is based on 2 main factors. The 1st is the elemental material. Platinum RTD could be utilized up to 650degree Celsius (i.e. 1202 degree F). The temperature rating of other materials is much lower and varies from one material to another. The 2nd factor that determines the temperature rating is the probe construction. All of these different styles use construction aspects that make them ideal for use in all of these styles. No single style fits all types.

 

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What Is An RTD Thermowell, Its Characteristics, Types, & Selection Criteria?

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Uses of Thermowell in Different Environments and Their Types!

How To Select The Most Suitable Thermowell For Your Application Based On Different Selection Criteria?

Call The Experts @Heatcon Sensors To Get Support With Your Selection for The Most Suitable Type of Temperature Sensor for Your Application!

A thermowell is a device that is used to protect a temperature sensor from the environment. It is typically made of stainless steel or other corrosion-resistant material, and it has a flared end to allow for easy insertion of the sensor. The thermowell also has a small borehole that allows the sensor to be mounted flush with the bottom of the well. This ensures that the sensor is in direct contact with the medium being measured. Thermowells are often used in high-temperature or high-pressure applications, or in applications where the sensor must be replaced frequently.

Uses of Thermowell in Different Environments and Their Types!

Thermowells are used in a variety of applications, including in process and boiler vessels, to measure the temperature of liquids and gasses. They are also used in pipelines, tanks, and other vessels where it is not practical to install a sensor directly into the process. Thermowells are available in a variety of shapes and sizes, and they can be customized to meet the specific needs of the application. These are of three main types based on the design of its stem as follows:

  • Straight Thermowell: These are the simplest and most economical type. They’re best suited for applications where the process conditions are relatively benign. However, this design is not well suited for high-velocity applications or applications with a large temperature differential between the well and the process.
  • Stepped Thermowell: These are more robust than straight thermowells and can withstand greater process pressures and temperatures. They’re often used in high-pressure or high-temperature applications. It is designed to minimize the effects of high velocity and large temperature differentials.
  • Tapered Thermowell: The most common type of thermowell is the tapered type, which is designed for use with RTD temperature sensors. The taper of the well allows for the sensor to be inserted into the well and then held in place by friction. It is designed for applications with very high velocities or very large temperature differentials.

 

How To Select The Most Suitable Thermowell For Your Application Based On Different Selection Criteria?

There are a few key factors to consider when selecting the most suitable thermowell for your RTD temperature sensor requirement as follows:

  • Material Selection: The most common materials used for thermowells are stainless steel, brass, and bronze. Stainless steel is the most popular choice because it is the most corrosion resistant. Brass and bronze are less popular because they are not as resistant to corrosion.
  • Bore Size & Length: The length and diameter of the thermowell should be based on the application. For example, if the sensor is inserted into a pipe, then the thermowell should be the same size as the pipe. The diameter of the thermowell should also be considered. A larger diameter thermowell will be more resistant to vibration and will have a longer life.
  • Connection Type: The type of process connection is also important. The most common type of connection is a screw-type. This type of connection is easy to use and is common in small diameter thermowells. A weld-type connection is more difficult to use but is stronger and can be used in larger diameter thermowells.

Call The Experts @Heatcon Sensors To Get Support With Your Selection for The Most Suitable Type of Temperature Sensor for Your Application!

If you are unable to make a selection of the most suitable temperature sensor and thermowell combination, don’t hesitate to consult the experts at Heatcon Sensors, a leading manufacturer of all types of high-quality temperature sensing devices, who can even actually be able to customize one for you after learning your specific application needs.

What Are RTD Temperature Sensor Elements, Their Types, & Their Benefits?

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Types of RTD Temperature Sensors & Their Main Advantages?

An RTD temperature sensor is a type of resistance based temperature sensor that uses a resistive element to accurately and precisely measure temperature in extremely high & low temperature applications. The resistive element, usually made of metal such as platinum, changes resistance in response to changes in temperature. This change in resistance is used to determine the temperature of the object or substance being measured. RTD temperature sensors are accurate and stable, making them ideal for use in critical industrial applications. RTD temperature sensors are also generally more rugged and durable than other types of temperature sensors. RTD temperature sensors are used in a wide variety of applications, including industrial and commercial process control, HVAC, and medical industry.

Types of RTD Temperature Sensors & Their Main Advantages?

There are two main types of RTD temperature sensor elements: thin-film and wirewound. Both have their own advantages based on your specific application requirements as below:  

  • Thin-film RTD sensor elements are made using the most advanced technology called photolithography by depositing a thin layer of conductive material onto a substrate. These elements are typically smaller and more accurate than wirewound elements, but they are also more fragile and expensive. The advantages of thin-film sensor elements include:
    • They are more accurate and small in size and quick response time.
    • They have lower thermal mass.
    • They are less susceptible to vibration and shocks.
    • They are more stable over time.
    • They are ideal for critical applications.
  • Wirewound RTD sensor elements are made by winding a thin wire around a substrate, typically glass or ceramic. These elements are typically less accurate than thin-film elements, but they are also more rugged and less expensive. The advantages of wirewound sensor elements include:
    • They are ideal to operate in a wider temperature range with great accuracy and precision.
    • They are known for their integrity and stability and are immune to the effects of vibration and shock, making them ideal for applications where these factors are present.
    • They offer excellent precision and accuracy, making them perfect for applications requiring precise temperature measurements.
    • They are highly repeatable, meaning you can rely on them to provide consistent results time after time.
    • They offer long-term stability, meaning they will maintain their accuracy and repeatability even after years of continuous use.
    • They are easy to install and use making them a great choice for applications where ease of use is a priority.

Contact Heatcon Sensors’ Expert Team To Decide Which Type Of RTD Temperature Sensor Element Is Most Appropriate for Your Industrial Process? 

Depending upon the application type, industry, and size, if accuracy is your top priority, then a thin-film RTD sensor element is the way to go. If ruggedness and affordability are more important to you, then a wire wound RTD sensor element is the better choice. If you still remain confused about your selection, don’t hesitate to consult with experts at Heatcon Sensors who are industry leaders in manufacturing all types of digital temperature sensors and temperature sensing devices which can also be customized as per your specific industry needs.

RTD Elements – The Most Widely Used Core Temperature Sensing Technology Today!

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Importance of Thin Film RTD Element Design!

Heatcon Sensors – The Industry Leaders in Manufacturing High-Quality Custom-Design RTDs For Most Accurate Temperature Readings!

If you’re looking for a reliable and accurate way to measure temperature, you can’t go wrong with a resistance temperature detector, or RTD. RTD elements are made of a material with a known resistance that changes with temperature, making them ideal for precision measurement. It is nowadays considered as a core temperature sensing technology widely used in temperature sensor assemblies and RTD probes. RTDs are generally made from different materials such as copper, nickel, platinum, and gold.

There are many different RTD element designs, but they all work on the same principle. As the temperature of the element changes, so does its resistance. By measuring the resistance, you can accurately determine the temperature of the element. RTD elements are used in a variety of applications, from industrial process control to consumer electronics, and HVAC systems. They’re well-suited for temperature measurement because they’re highly accurate and stable over a wide range of temperatures.

Importance of Thin Film RTD Element Design!

There are many factors to consider when designing an RTD element, such as material selection, resistance value, size, wiring and connection type. 

  • The most important factor in RTD element design is the material selection. The material must have a high resistivity in order to accurately measure temperature. The most common materials used for RTDs are platinum, nickel and copper. 
    • Platinum is the most expensive material, but it is also the most accurate as they provide the best linear resistance change. Platinum RTDs can measure temperatures up to 800 degrees Celsius. 
    • Nickel is less accurate than platinum, but it is cheaper and can measure temperatures up to 500 degrees Celsius. 
    • Copper is the least accurate of the three materials, but it is the least expensive and can measure temperatures up to 300 degrees Celsius.
  • The resistance value is important because it determines the accuracy of the temperature measurement. When selecting the material for an RTD element, it is important to consider the accuracy requirements of the application. For applications that require high accuracy, such as HVAC or automotive, platinum is the best choice.
  • The size and wiring of the RTD element also need to be considered, as they can impact the accuracy of the temperature measurement.

Heatcon Sensors – The Industry Leaders in Manufacturing High-Quality Custom-Design RTDs For Most Accurate Temperature Readings!

If you are searching for the best type of RTD sensor for precise temperature measurement, an RTD is a great choice. With its high accuracy and stability, an RTD can help you get the most accurate temperature readings possible. If you are unsure which RTD element will work best for your application, you should contact experts at Heatcon Sensors who can guide you with your selection, and also you can expect the best custom-made solution to exactly meet the specific needs of your industrial application. The Heatcon Sensors team is highly experienced in customizing the thin film RTD element designs which offer the best value for your money.

4 Types of Temperature Sensors Commonly Used In the Industry for Temperature Measurement!

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NTC Thermistor a.k.a. Negative Temperature Coefficient Thermistor

RTD Sensor OR Resistance Temperature Detector

Thermocouples 

Semiconductor OR Integrated Circuit Temperature Sensors 

Temperature sensors are one of the most important tools that scientists and engineers use to measure the temperature of the objects around us. From industries needing controlled environments for carrying out different processes to fire safety equipment, temperature sensors are so much so important these days to ensure the optimum temperatures at all times. They come in all shapes and sizes, and each one is designed to measure temperature in a different way. Each type of sensor has its own advantages and disadvantages, so it’s important to choose the right sensor for the job. No matter what type of temperature sensor you use, it’s important to calibrate it regularly to ensure accuracy. Temperature sensors are an essential tool for anyone who needs to measure temperature, whether they’re scientists, engineers, or even just amateur hobbyists. Here, we are going to discuss 4 Types of Temperature Sensors Commonly Used In the Industry for Temperature Measurement.

  1. NTC Thermistor a.k.a. Negative Temperature Coefficient Thermistor

A Negative Temperature Coefficient thermistor, or NTC thermistor, is a type of resistor that decreases in resistance as temperature increases. The resistance of an NTC thermistor decreases as temperature increases because the increase in thermal energy causes the atomic particles in the material to vibrate more, which reduces the number of available electrons. The resistance of an NTC thermistor can be used to measure temperature in applications where high accuracy is required as even small changes in temperature can cause changes in resistance of the thermistor in a big way. They are commonly used in temperature sensing applications which operate in the range of anywhere between -50 0C and 250 0C.

  1. RTD Sensor OR Resistance Temperature Detector

RTDs or resistance temperature detectors are made of metal, and they work by measuring the resistance of the metal to changes in temperature. The choice of the metal for creating an RTD is responsible for its accuracy and stability. While platinum based RTD is most stable and accurate, the copper and nickel based RTDs have lower costs and are little unstable for repeated use. RTDs are used in a variety of applications, including HVAC, automotive, and industrial control. RTDs are more accurate than other types of temperature sensors, and they are also more stable over time. However, RTDs are more expensive than other types of temperature sensors. If you need a temperature sensor for your application, an RTD may be the best option. They are applicable in systems where high accuracy linear output is needed and platinum based RTD operates between a great range of -200 0C and 600 0C.

  1. Thermocouples 

A thermocouple is a temperature sensor that consists of two dissimilar metals that are joined together at one end. When the two metals are at different temperatures, a voltage is generated. This voltage can be used to determine the temperature difference between the two metals. Thermocouples are very common in industrial applications. They are used to measure the temperature of things like ovens, furnaces, and pipelines. Thermocouples can also be used to measure the temperature of the environment. They have the widest temperature range and operate between -200 0C to 1750 0C. 

  1. Semiconductor OR Integrated Circuit Temperature Sensors 

Semiconductor temperature sensors are used to measure the temperature of semiconductor materials and electronic devices. These sensors are made from materials that have a high thermal conductivity, such as silicon or germanium. Semiconductor temperature sensors can be used to measure the temperature of electronic devices, such as CPUs and GPUs. These sensors are accurate and reliable, and can be used to monitor the temperature of devices in real-time. They are slowest in their responsiveness and have the lowest accuracy. They offer linear response to temperature changes and operate between the temperature ranges of -70 0C to 150 0C. 

For the best temperature sensors and to understand what type of temperature sensor works best for your industry, you may contact one of the experts from Heatcon Sensors; a leading global manufacturer of quality temperature sensors.

A molten metal thermocouple is a temperature sensor that is used in a variety of industrial applications to control temperature. There are many different types of molten metal thermocouples, each with its own unique set of characteristics. The most common type of molten metal thermocouple is the Bobbin Heaters which is made up of two different metals that are placed in a ceramic cup. The two metals are then connected to a power source and the resulting voltage is used to measure the temperature of the metals. Bobbin Heaters are often used in chemical immersion heater and hot air blower.

Another type of molten metal thermocouple is the chemical immersion heater which is often used in industrial applications to control the temperature of a variety of different liquids. Whereas, the hot air blower is often used in humidity chambers to control the humidity levels which is why most industrial applications of humidity chambers prefer to use a hot air blower.

Resistance Temperature Detector (RTD) – Frequently Asked Questions

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A Pt100 Class A RTD is recommended to use a 4-wire connection, why is it so?

How do 2, 3, or a 4-wire connection differ?

How to choose the alpha (TCR) curve?

The following article covers the frequently asked questions regarding RTD in various aspects.

A Pt100 Class A RTD is recommended to use a 4-wire connection, why is it so?

A 4-wire based connection is able to compensate entirely for the effect of the wire resistance of the cable circuit. In a connection using a 2-wire or even a 3-wire it becomes necessary to program in a manual way the value of the cable resistance that’s measured as a parameter to correct the displayed readout.

But despite this, it is observed that the parameter will hold good only for the temperature that was prevalent at the moment the cable’s resistance was measured. With change in the ambient temperature, the accuracy of the measurement circuit is lost.

In comparison, a 4-wire connection is capable of compensating for changes in ambient temperature.

Since Pt100 RTDs of type Class A are specifically meant to measure temperature accurately, it becomes really important that the implementation of the wire connection be made as a 4-wire connection.

How do 2, 3, or a 4-wire connection differ?

It is a norm for RTDs to be made available in a 2, 3, or 4-wire connection configuration.

Choosing the most suitable configuration that will hold good for an application is dependent on numerous factors, but it is equally important that there’s a match between instrumentation and sensor configuration, else the effect of the circuitry that cancels out the wire resistance will have no bearing.

Factors that cannot be ignored:

  • Installation cost – use of higher number of wires will incur a substantial cost
  • Space consumption – use of fairly large number of wires consumes that much more space
  • Accuracy related – 2-wire connection configurations are reliable only when used with elements having high resistance.

1. Construction of 2-wire connection RTD

2-wire connection RTD’s temperature reading is artificially on a higher side as other than its element resistance, the lead wires resistance also gets added along.

2. Construction of 3-wire connection RTD

The result displayed by an RTD that’s on a 3-wire connection configuration is accurate only if the lead wire resistance error is negated, and this can happen only if the instrumentation is able to measure the true resistance of the 3-wire configuration.

There is a cancellation of the lead wire resistance error only when all of the lead wires are of similar resistance. When the 3 wires in use are of the same length, composition, and AWG, the result is that the lead-wire resistance will have a match of around 5%.

3. Construction of 4-wire connection RTD 

It depends on the ability of the instrumentation in being able to determine the true resistance of the 4-wire connection for the resistance to be cancelled out from the RTD’s result.

The lead wire resistance error will be cancelled out from a 4-wire connection RTD’s resistance measurement when the 4 wires in use are of the same length, composition, and AWG.

4. Are the 2, 3, and 4-wire connection RTD configuration interchangeable?

  • A 4-wire connection RTD can be used as a 3-wire connection RTD by not utilising one the leads, or in other words by tying it off.
  • Likewise, 4-wire connection RTDs can be used as a 2-lead RTD after shorting the leads that are in common.

It needs to be noted that when common leads are shorted, it eliminates the benefit that a 4-wire connection brings in by cancelling out the lead wire resistance.

How to choose the alpha (TCR) curve?

TCR or Temperature Coefficient of Resistance is the average change in resistance that the sensing element will undergo over a particular temperature range like between 0℃ to 100℃.

The value is considered to be a characteristic of the material the element is made of and is not dependent on the base resistance. It’s unit of measurement is Ohms/ohm/C

Example:

A probe can read 100 ohms at 0°C, but at a different temperature suppose at 100°C, the .00385 probe will show a reading of 138.5 ohms and the .00392 probe will show a reading of 139.20 ohms.

  1. Resistance curve mainly depends on instrumentation. Refer to your instrumentation manual for acceptable Resistance Temperature Detector (RTD) input types.
  2. Common TCRs include:

 

With over three decades of expertise in temperature sensor and heater manufacturing, Heatcon Sensors provides a high level of quality, accuracy, and an unbeatable commitment to customer support.

If you are interested in knowing more about RTDs, thermocouples, thermocouple probes or thermocouple wires that we manufacture, and also of the other services we offer, please feel free to call us on +91 9844233244.

What is a Resistance Temperature Detector (RTD)? Understanding RTD Types, Styles, Power Supply, Transmission and Wiring Arrangements

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RTD Types

RTD Styles

RTD Wiring Arrangements

Power Supply for RTD

Transmission of RTD signals

Advantages

Disadvantages

A resistance temperature detector (RTD) also known as resistance thermometer because it helps in measuring temperature which is a measure of the output resistance.

The elementary operation of an RTD is that with decreases or increases in the temperature of an object, the resistance must also decrease or increase proportionally. The main differentiator between a Thermistor and a RTD is that, a thermistor utilises a polymer or ceramic material when it comes  to sensing, whereas the sensing element utilised in an RTD is a metal. As platinum is the most widely used metal in the field of manufacturing RTD’s, the device is also called Platinum Resistance Thermometers (PRTs).

RTD Types

RTDs can be classified broadly depending on the different sensing elements that have been used. Copper, Platinum, and Nickel are the most widely used sensing elements. Among these, Platinum is regarded the best as it has the widest temperature range. Platinum type RTD is also well known for its interchange ability when compared with nickel and copper and also offers the highest time stability. It is also possible to use PRTs in unsuitable environments where reducing atmospheric metallic vapours is the priority. PRTs have extensive use cases in industrial applications; as a PRT can help in measuring temperatures that are as high as 600℃, while Nickel and Copper only have a limit of measuring temperatures to a maximum of 400℃.

RTD Styles

RTDs are manufactured and are made available in several options with single, double, or even triple windings, each one separated electrically. To allow two independent measuring circuits to track or measure the same temperature it is important to use more than one winding, this also permits more than one measurement to be done by only installing a single sensor. Nevertheless, to increase both the conduction error along with the response time, extra mass has been introduced to the sensor by the addition of windings along with encapsulating materials, and their associated support. This process of utilising separate sensors provides mechanical independence during maintenance.

RTDs are usually a tip-sensitive, spring-loaded construction that has a 1/4-inch-diameter sheath.

RTD Wiring Arrangements

RTDs are available with either two, three, or four output wires that are required in order to connect to the secondary instrument.  The different wiring arrangements are specifically designed in order to reduce or completely get rid of any errors that could have been introduced as a result of resistance changes of the lead wires due to changes in temperature that they too have to experience. 

Generally, a three-wire or a four-wire system that has paired lead wires is used in RTDs that are in electrical equipment.

In most cases, Copper is the best choice in terms of lead wires for all the arrangements. For a particular RTD, the lead wires have the same length and are of the same gauge, this helps in ensuring they run within the same conduit.

Power Supply for RTD

There is a need for an electric DC power supply in order to provide current to the resistance­ measuring circuit. A secondary instrument is generally utilised  in applying the required power supply. In some cases, when the secondary instrument happens to be a transmitter providing a current output of (4-20) mA, then the resulting power is generally carried using two output wires of the transmitter.

Transmission of RTD signals

Among all the instruments used for transmitting RTD signals, the transmitter is the most widely used. It is possible to mount a transmitter either locally, or even on an enclosed rack. A local transmitter can be supplied along with it as a complete assembly by simply mounting it on a Thermowell. Among the many popular RTDs used, the “Smart” transmitter is the most widely used RTD transmitter.  In the case of a typical “Smart” temperature transmitter its is extraordinarily versatile: it is appropriate for Nickel and Platinum RTDs; 100, 200, or 500 ohm Platinum sensors, etc; 2, 3, or 4 lead wire arrangements. It is possible to use the same instrument as a thermocouple transmitter, which is compatible with any thermocouple combination that is available commercially.

Advantages

    • Sufficiently suitable for measurements that are remote 
    • Provides high accuracy
    • Helps in the measurement of very narrow spans
    • Amazing stability along with reproducibility 
    • Also offers Interchangeability
    • Has the capability of matching close tolerances in case of temperature difference measurements.

Disadvantages

    • It can be sensitive to signal noise
    • Sensitive in terms of mechanical damage
    • It can cost a lot
    • Lead wire resistance compensation is needed 
    • It is sensitive to self-heating errors
    • Once damaged, it is not repairable in most cases
    • It is not recommended for bare use inside electrically conducting substance
    • There is always a need for a Power supply.

With over three decades of expertise in temperature sensor and heater manufacturing, Heatcon Sensors provides a high level of quality, accuracy, and an unbeatable commitment to customer support.

If you are interested in knowing more about thermocouples, thermocouple probes or thermocouple wires that we manufacture, and also of the other services we offer, please feel free to call us on (+91- 9844233244).