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Hi CircuitLab community, I am looking to design a body temperature sensor using thermistors, several amplifiers and a filter circuit. I have been trying to find something to use as a thermistor in CircuitLab but I haven't found anything. Is there a feature that allows me to do this or use something else instead?

I need to design a device that can detect skin temperature, amplify, and filter the signal to construct a heat stroke monitoring device. Anyone with suggestions, please feel free to reach me I would be more than appreciative!

Thanks for any help you can provide!

-Drexel University Biomedical Engineering Student

Hi rmd92,

Welcome to CL.

You can build a behavioural model of a thermistor like this:

https://www.circuitlab.com/circuit/ch23n3/behavioural-thermistor-01/

This was done before CL introduced parameters and I haven't revised it to use them but the circuit as is uses voltage sources to implement what would normally be done using parameters in an expression to define the resistance vs temperature function.

https://www.circuitlab.com/docs/expressions/

https://www.circuitlab.com/docs/circuit-elements/#behavioralsources

https://www.circuitlab.com/blog/2013/10/01/circuit-parameters-to-make-schematics-smarter/

The expression used to define the R vs. T curve is based on the B or β parameter equation in:

http://en.wikipedia.org/wiki/Thermistor

The datasheet for your chosen thermistor should supply the coefficients.

Hi Signality,

Thanks so much for your welcome and your response. I have one question, when I edit the formula for the NTC where (temp) is and put a temperature value in there, CL does not allow me to simulate it. I'm a little bit unsure where to plug in my values into these equations to get the desired output.

Again, thanks so much for your support I really appreciate it.

Here's a proper thermistor model:

https://www.circuitlab.com/circuit/h55r3m/thermistor-beta-model/

:)

Thank you very much for your help signality.