✔ Ntc Thermistor Linearization

Ntc Thermistor Linearization

- April 04, 2018

A thermistor is a resistor whose resistance varies with temperature figure 1. I was able to get a reasonable straight line but opted for three piece wise lines to achieve greater accuracy.

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3 beta a parameter which is a property of the thermistor material.

Ntc thermistor linearization. When using ntc thermistors resistance decreases as temperature increases. In many ways thermistors are a great sensor. An example thermistor linearization circuit is shown in figure 9 and its equivalent resistance versus temperature profile is shown in figure 10.

The technique utilizes two identical thermistors and two resistors. The high sensitivity of an ntc thermistor makes it an ideal candidate for temperature sensing ap plications. Parallel resistor suppose youve been asked to design a linearized thermistor circuit with a temperature range centered around 25 deg c.

Since temperature measurement is defined in terms of the thermal expansion of materials people have come expect their temperature readouts to be linear with respect to same figure 1 curve b. Voltage mode and resistance mode. The resistance across the thermistor is relatively high in comparison to the rtd element which is usually in the hundreds of ohms range.

Typically these thermistors are used as resistive temperature sensors and as current limiting devices. The output voltage of the thermistor is modeled using the first order and the third order polynomial fitting equations. Typically the 250c rating for thermistors is from 1k up to 10m.

In a paper 4 the linearization of ntc thermistor using voltage divider linearizing circuits such as a wheatstone bridge and a serial parallel resistive voltage divider is examined. The resis tance versus temperature response of a 10k ntc thermistor is shown in figure 3. Cheap tough small and accurate.

The thermistors that i use have a negative temperature coefficient ntc which means their resistance reduces as their temperature increases. Software linearization techniques for thermistors interfacing an ntc thermistor to a computerized data acquisition system requires a resistance to voltage or current converter bridge voltage. This note discusses how a common ntc thermistor may be linearized to simplify calculations.

An ntc thermistor is a resistor that has a negative temperature coefficient hence ntc. R thermistor resistance at t oo and. These low cost ntc sensors are normally used for a temperature range of 40 0c to 300 0c.

There are two basic ways to linearize a thermistor in hardware. In this example the linearized ntc r25 is 10 kw rs is 5 kw and rp is 10 kw. Ntc negative temperature coefficient the resistance decreases as temperature increases.