Resistance Temperature Detectors (RTD)

Understanding an application's performance requirements, such as operating temperatures, accuracy and repeatability demands, material compatibility issues, and environmental conditions, are crucial to designing the best RTD temperature sensor solution.  In addition, many applications require special quality validation, testing, and certifications.

Durex Industries is prepared to provide the best RTD temperature sensor for your application requirements. Accurate, repeatable and robust RTD sensor (resistance thermometers) assemblies manufactured by Durex Industries provide fast temperature response and can be applied in most temperature measurement and control applications.

What are Resistance Temperature Detectors?

RTD sensors are thin film or wire wound resistor elements that use the Ohm resistance value to indicate a temperature value. The resistance simultaneously increases with temperature increase and vice versa.

Each RTD has a “calibration,” which indicates a specific base resistance value at a specific temperature (such as 100 Ohms at 0C) and a specific resistance vs temperature curve (DIN curve, JIS curve, etc).

Advantages of RTD Sensors Over Other Temperature Sensors

Applications for Resistance Temperature Detectors

Industrial RTD temperature sensors are used in any application that requires temperature accuracy, the stability of readings over time, and repeatability of reading accuracy over time. They’re also used where application temperature ranges are -200C to 650C, as well as where high sensitivity to temperature change is not required.

RTD sensors are used for virtually every industry, but you typically find them in:

Contact Durex Industries Today for RTD Temperature Sensors

All of our RTD sensors are quality tested and validated to meet your requirements. As a leading RTD temperature sensor manufacturer, our experienced team will work with you to develop the best, most economical custom RTD sensor solution for you.

To find out if resistance temperature detectors are right for your applications, view our temperature sensor element selection guide, or contact us today.

 

Resistance Temperature Detectors-Leadwire

RTD with Lead Wire or Fixed Fittings

The R1 RTD sensor style with probe & lead wire. R2 RTD sensor style with fixed fitting. The RTD sensor of choice for temperature measurement applications due to the accuracy and long term stability.

Adhesive Resistance Temperature Detectors

Adhesive Backed RTD

If the surface being measured for temperature cannot be penetrated or if space limitations require it, Durex can manufacture a Resistance Temperature Detector with an adhesive patch for direct surface mounting.

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Adjustable Depth RTD Sensors

Adjustable depth RTD sensors with compression spring and bayonet lock-cap or flexible stainless steel armor cable with rotating bayonet lock-cap.

Air Resistance Temperature Detectors

Air RTD

The perforated tip of the air resistance temperature detector is designed for rapid monitoring of airflow temperature in various applications. Small film sensing elements used in these housings can detect incremental changes in temperature more quickly than conventional housings.

Diesel Engine Temperature Sensors

Diesel Engine Temperature Sensors

Temperature monitoring in today’s sophisticated engines is critical for proper engine control module (ECM) operation to ensure high fuel efficiency and low emissions levels in diesel engines, extreme racing vehicles and aircraft jet engines. Our RTDs, Thermocouples, IC sensors and Thermistors are specifically designed to perform in rugged harsh environments.

Flexible Resistance Temperature Detectors

Flexible RTD

When a resistance temperature detector needs to "snake" through an installation because of space limitations or other factors, Durex Industries manufacturers flexible resistance temperature detector elements with overbraid shielding or armor to suit the specifics of your temperature sensing application.
Hand Held Resistance Temperature Detectors

Hand Held Temperature Probes

Durex manufactures a line of multi-purpose hand held resistance temperature detector probes for foodservice, industrial process, and laboratory applications. RTD temperature probe features include handles of stainless steel, Teflon, or plastic and coil cord leadwires that can be constructed to withstand ambient temperatures up to 400°F.

Immersion Resistance Temperature Detectors

Immersion RTD

For applications requiring immersion into any liquid or semi-solid, Durex will supply resistance temperature detector probes in protective thermowells or protection tubes, with sealed terminal heads.

Transmitter Resistance Temperature Detectors

Integrated Transmitter RTD

This unique line of integrated transmitter resistance temperature detector probes combine an industry standard 4-20mA transmitter with a matched high accuracy RTD in a compact, hermetically sealed assembly.

Melt Bolt Resistance Temperature Detectors

Melt Bolt RTD

RM style resistance temperature detector melt bolt sensor assemblies are designed for dependable temperature measurement of the plastic melt stream within extruders and injection molding equipment.

Compression Fitting Resistance Temperature Detectors

RTD with Compression Fitting

RC style straight run, 45° and 90° bend resistance temperature detector compression fitting sensors are available in a wide variety of sizes and styles.

Fixed Bayonet Resistance Temperature Detectors

RTD with Fixed Bayonet

RB style straight run, 45° and 90° bend resistance temperature detector fixed bayonet sensors are available in a wide variety of sizes and styles.

Probe-Plug Resistance Temperature Detectors

RTD With Probe & Plug

R3 style resistance temperature detector with stainless steel or Inconel sheath and various plug termination options. A wide variety of element types, wiring configurations and sheath diameters are available.

Terminal Head Resistance Temperature Detectors

RTD Probe With Terminal Head

R4 style RTD assembly with probe, screw cover terminal head and NPT fitting. This assembly is used where protection for the termination is a consideration and can be designed for an outdoor application or with an integral transmitter.

Thermowell Resistance Temperature Detectors

RTD Thermowells

RW style resistance temperature detector thermowells are available in various element types and wiring configurations. Cast iron or aluminum screw cover heads are commonly used to terminate the thermowell assemblies, however, other head options are available.

Sanitary Resistance Temperature Detectors

Sanitary RTD

RS style resistance temperature detector sensor probes with sanitary connections are commonly used in the food and dairy industries. These fittings are welded to the stainless steel sheath and polished to meet 3-A Sanitary Council Standards.

Silicone Resistance Temperature Detectors

Silicone RTD

Utilizing the same technology as a sealed silicone rubber heater, Durex offers a surface mount resistance temperature detector (RTD) sensor for direct mounting to flat or curved surfaces.

Surface Mount Resistance Temperature Detectors

Surface Mount RTD

RSM style surface mount resistance temperature detectors can be supplied with block surface mount, spade type surface mount or adhesive patch mounting hardware. Fiberglass, Mica/Fiberglass, Teflon or PVC leadwires with various braiding or armor cable shielding options are available.

Teflon Coated Resistance Temperature Detectors

Teflon Coated RTD

Resistance temperature detectors are available with Teflon coated sheaths for applications that require contact temperature measurement in corrosive or chemical environments. The Teflon coating can be applied directly to the sheath of the RTD, providing protection while minimizing effects to response.

Resistance Temperature Detector Specifications

Unless otherwise specified, Durex's RTD assemblies include photo-lithographically structured, high-purity platinum thin-film elements laser trimmed to precise resistance values. These sensors feature brief response times, excellent long term stability, low self heating and excellent resistance to vibration and temperature shocks.

Thermal Response Time
The response time T0.63 is the time the sensors need to respond to 63% of the change in temperature. The response time depends on the sheath dimensions, but can be as low as 1.2 seconds.

Long Term Stability
The change of ohmage after 1,000 hours at maximum operating temperature amounts to less than 0.03%.

Self Heating
To measure the resistance, an electric current has to flow through the element, which will generate heat energy resulting in errors of measurement. To minimize error, the testing current should be kept low (approximately 1mA for Pt-100).
Temperature error ΔT = RI²/E with:
E = self-heating coefficient in mW/K
R = resistance in kΩ
I = measuring current in mA
The self-heating coefficient (E) for the standard elements used in Durex RTD assemblies is 4 mW/K in air and 40 mW/K in water.

Measuring Current
Measurement current causes heating of the platinum thin-film sensor. The resulting temperature error is given by:
ΔT = P/E with the power loss P = I2R, and the self-heating coefficient E in mW/K.
The amount of thermal transfer from the sensor in the application determines how much measuring current can be applied. There is no bottom limit of the measurement current with platinum thin-film. The measurement current depends highly on the application in use.
We recommend at:
100Ω: typically 1mA, maximum 5mA
500Ω: typically 0.5mA, maximum 3mA
1000Ω: typically 0.3mA, maximum 2mA
2000Ω: typically 0.2mA, maximum 1mA

Nominal Values
The nominal or rated value of the sensor is the target value of the sensor resistance at 0°C. The temperature coefficient α is defined as α =  (K-1) and has the numerical value of 0.00385 K-1 according to DIN IEC 751.

In practice, a value multiplied by 106 is often entered: TCR = 106 x (ppm/K)

In this case, the numerical value is 3850 ppm/K.

Temperature Characteristic Curve
The temperature characteristic curve determines the dependence of the electrical resistivity on the temperature. The following definition of the temperature curve according to DIN EN 60751 standard applies:

 

Tolerance Classes

Class ± limit deviations in °C (K) IST AG designation Temperature range
DIN 60751, class B 0.30 + 0.005 x |T| B -200°C to 850°C
DIN 60751, class A 0.15 + 0.002 x |T| A -90°C to 300°C
⅓ DIN 60751, class B 0.10 + 0.0017 x |T| Y -50°C to 150°C

|T| is the numerical value of the temperature °C without taking into account either negative or positive signs.
Special selection of sensors upon request (pairings, groupings, special tolerances).

Calibration Services
Durex RTD calibrations are fully traceable to the National Institute of Standards and Technology (NIST) and are useful for defining the exact temperature coefficient of the sensor. For sensor applications below 32°F (0°C), a cryogenic range calibration is recommended. Certificates are supplied with all calibrations. Printed tables of interpolated values are only supplied with cryogenic range calibrations.

Style: R1L, R2L, R3L, R4L - The maximum rated temperature for these four styles is 500°F. Typically they are constructed with Teflon leads and the lead end is protected with an epoxy seal. This epoxy seal provides a moisture resistant barrier.

Style: R1M, R2M, R3M, R4M - The maximum rated temperature for these next four styles is 900°F. They are constructed with high temperature fiberglass insulated conductors. The lead end is sealed and protected with a high temperature cement.

Style: R1P, R2P, R3P, R4P - The maximum rated temperature for these last four styles is 1200°F. Their construction features highly compacted magnesium oxide insulation. Nickel conductors provide for extended temperature ratings and harsh environments.

 

Available Resistance Temperature Detector Elements

Code Element Type Temperature Coefficient Tolerance at 0°C
A 100 ohm Platinum .00385 .1%
B 100 ohm Platinum .00385 .06%
C 100 ohm Platinum .00385 .03%
D 500 ohm Platinum .00385 .1%
E 1000 ohm Platinum .00385 .1%
F 2000 ohm Platinum .00385 .1%
G 100 ohm Platinum .00392 .1%
H 100 ohm Platinum .00392 .03%
J 120 ohm Nickel .00392 .5%
K 604 ohm Nickel Iron .00392 .5%

RTD Wiring Diagrams

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Custom Options Available - Contact us for Engineering Assistance.

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