TR67 & TR136 SERIES 15KOhm@25°C THERMISTOR SPECIFICATIONS

General Information   Interchangeability Tolerance and Accuracy   Steinhart-Hart Equation Coefficients   Resistance vs Temperature (R-T) Table and Data Download

 General Information

Thermistor is a generic term describing a semiconductor device that exhibits an electrical conductivity that is highly sensitive to temperature. The name was derived from the words, "thermally sensitive resistor". These devices may be either positive temperature coefficient (PTC) or negative temperature coefficient (NTC) with respect to their resistance characteristics with temperature.

Our thermistor sensors have an NTC type resistance versus temperature characteristic. In addition, they have a matched resistance versus temperature curve and are interchangeable from one thermistor to another per the specified tolerance.

The tolerance used for our thermistors is typical in the industry and represents the best compromise between price and what is achievable with good manufacturing practices. Improved interchangeability can be provided at a higher cost. Sensors could also be sorted using third party calibration laboratories, or your own in-house calibrator, to ensure greater accuracy for each sensor installation (controller/sensor combination). Calibration is also useful when two sensors are attached to the same controller, since sensors that match can be selected. Regardless, the tolerances shown are the extreme, as required for engineering calculations. Most sensors are well within the Interchangeability Tolerance shown below.

Our temperature controllers are designed for "end point stability." Generally, for any given set point, control can be matched from controller to controller by making minor adjustments to the set point. With our PC compatible controllers, there is usually an Input Offset feature that can be used to make minor adjustments to the temperature being reported by the sensor.

Base Resistance at 25°C is 15,000 Ohms.

Interchangeability Tolerance and Accuracy

Note that the tolerance specifications of the sensor do not affect end point temperature control and temperature stability. They affect the accuracy of the temperature being "reported" by the sensor when using a PC compatible temperature controller, or a temperature controller with a front panel display. Our controllers are designed for excellent end point temperature control, but they are not meant to be calibration grade instruments (which are far more expensive). To improve the accuracy of the temperature reported by any of the sensors listed below, calibrate the sensor/controller combination to an in-house or third party standard. If you have a question about the thermistor tolerance specifications as related to your requirements, or about calibration, please  . There are many calibration techniques and tools.

Interchangeability Tolerance and Accuracy:

• TR67 Series: ±1.0°C within 0°C to 100°C (approximately ±2°F within 32°F to 212°F)
• TR136 Series: ±0.1°C within 0°C to 70°C (approximately ±0.2°F within 32°F to 158°F)
• Inquire for sensors that provide a ±0.2°C tolerance.

The Steinhart-Hart polynomial is 1/T = A₁ + A₂(ln(R)) ... + A_N(ln(R))^N and this formula is generally reduced to the formula shown below. 

1/T = A + B(ln(R)) + C(ln(R))³

"T" is the temperature and "R" is the resistance and the coefficients are A, B and C.

The following TR67 series thermistor coefficients are suitable for the Steinhart-Hart equation.

A: 1.0373E-03 
B: 2.332E-04
C: 8.39E-08