Omega's Precision Interchangeable Thermistor Sensors - Technical and Application Information

Thermistor Applications

Available in Linear and Non-Linear Versions
Temperature Range: -80 to 75 or 150°C Depending on Selection
Tight Accuracy: ±0.1C or ±0.2C Depending on Selection
Fast Response Time: Less Than 1 Second (63% Response in a Well stirred Oil Bath)
Available in Multiple Designs for Various Immersion, Air Monitoring, Surface Sensing or Other Applications
Provide High Level of Resolution (Many Ohms Per °C)
Available in 2252, 3000, 5000, 10000 or 30000 Ω/°C.

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Thermistors are available in Linear and Non-Linear varieties;

Non-Linear thermistors are typically two-wire sensors that have resistance vs. temperature charecteristics that are non-linear over their temperature range. These thermistors follow the Steinhart-Hart Equation and a set of constants to calculate temperature from their resistance. These thermistors are typically used with electronic instruments that contain circuitry set up specifically for the thermistor, or in a voltage devider circuit.

Linear thermistors are typically 3-wire devices with two individual thermistors in one package. When combined with specific series and shunting resistors, these sensors provide an output that is linear over a specific temperature range. These are typiclally used in laboratory applications.

Within their performance limits, thermistors can be a reliable and stable option for measuring temperature. The performance limits for Thermistors include:
© Temperature Range of -80 to 150°C (some lower depending on selection)
©Non-Linear Resistance vs. Temperature Curve (see Steinhart-Hart equation discussion below)
©Low Excitation Currents: Normally 15 Microamps.

Benefits Include:
©Large Resistance Changes per Degree for Good Measurement Resolution.
©Tight Accuracies Typically ±0.1°C or ±0.2°C Between 0 and 70°C
©Good stability
©Small Size = Fast Response to Changing Temperatures

Thermistors are typically used in applications where their large changes in resistance per degree allow for precise measurement of small temperature changes. This feature also provides the user with better resolution than do Thermocouples which change a few millivolts per degree or RTDs which typically change less than ½ of an ohm per degree. Check out the attached Specification Sheet for more technical and application information on Thermistors.