Questions concerning thermistors

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In summary, the conversation discusses questions about thermistors and their use in temperature actuated circuits. The speaker asks about the resistance value found on spec sheets and the meaning of the b-constant. They also inquire about the need for an amplifier or if the thermistor can be used directly with a zener to create a temperature actuated switch. The conversation ends with the speaker expressing their limited knowledge on the subject and asking for any helpful information or resources.
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I've got some rather simple questions concerning thermistors. First, in viewing spec. sheets I only see one resistance value. What is that value telling me? In some of the specs there is something called a b-constant. What is that? Does a temperature actuated circuit demand an amplifier to take the small changes in resistance and produce larger voltage fluctuations? or can you just use them directly in series with a zener to make a temperature actuated switch? Basically I know little more than the general idea that they vary their resistance with temperature. Any answers, information, etc. would be much appreciated. Thanx for your time and patience with my ignorance.
 
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  • #2
Most applications use the dR/dT----> dV/dT about a nominal value to drive a differential amp for proportional control, Or use the voltage drop and a windowed comparitor w/hystrerisis for on-off type control.
 
  • #3
Yea, all I need is an on-off type deal.
 
  • #4
If you have access to an national semi analog circuits handbook, there is a lot of good examples, otherwise, radio shack sells these small and really nice, circuit design handbooks, I think op-amps and comparators are in the same book, good designs that work and can be built quickly.
 

1. How do thermistors work?

Thermistors are temperature-sensitive resistors that change their resistance in response to changes in temperature. They consist of a ceramic or polymer material with a high temperature coefficient of resistance, meaning that their resistance changes significantly with even small changes in temperature.

2. What are the applications of thermistors?

Thermistors are commonly used in temperature measurement and control systems, as well as in electronic devices such as thermostats, thermometers, and heating elements. They are also used in automotive applications for engine temperature monitoring and in medical devices for body temperature measurement.

3. How do I choose the right thermistor for my application?

The most important factor to consider when choosing a thermistor is its temperature coefficient of resistance (TCR). This will determine how much the resistance will change for a given change in temperature. You should also consider the desired temperature range, accuracy, and response time for your specific application.

4. What is the difference between a thermistor and a thermocouple?

A thermistor is a type of resistor that changes its resistance with temperature, while a thermocouple is a temperature sensor made of two different metal wires that produce a voltage in response to temperature changes. Thermistors have a higher sensitivity and accuracy at lower temperatures, while thermocouples are better suited for higher temperature ranges.

5. How do I calibrate a thermistor?

To calibrate a thermistor, you will need a temperature reference source and a multimeter. First, measure the resistance of the thermistor at a known temperature using the multimeter. Then, compare this reading to the expected resistance from the thermistor's datasheet. Adjust the calibration of your device accordingly. It is recommended to perform multiple calibrations at different temperatures for greater accuracy.

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