4.7K Thermistor Temp OutPut in Deg C

Projects General Guidance
1

I have a 4.7K Thermistor and a 4.7K Resistor and I am looking for the equation to calculate the Temp Output in Deg C to display on an LCD.

I seem to be able to find examples using a 10K Resistor but from what I read I need to use the same size resistor as the Thermistor?

Could someone please provide a link as I've also used a Youtube video for "scaling a thermistor" but it is far from Accurate.

Thanks,

2

Do you have a datasheet for the thermistor?

3

Hi,
Did you google

4.7k thermistor temperature calculation

and

4.7 k thermistor arduino

Tom... :slight_smile:

4

TomGeorge:
Hi,
Did you google

4.7k thermistor temperature calculation

and

4.7 k thermistor arduino

Tom... :slight_smile:

Yes I googled it and it seemed always end in a blog or post around using a 100K or 10K thermistor.

It's the equations that don't seem right for the output. I'll post my sketch and see if you can pick the issue.

Thanks,

5

Hi,
The third google hits.

Has the conversion equation for 4k7.

You need to calculate the thermistor resistance from your analog input voltage.

Tom... :slight_smile:

6

AFAIK the sketch for different thermistor values is the same if the fixed resistor matches the thermistor value.
The ratio (output voltage on the tap) stays the same (if thermistor specs are the same).

http://playground.arduino.cc/ComponentLib/Thermistor2

The third sketch on this page has the option of entering a different value for VCC (it never is exactly 5.0volt).
And a value for the thermistor (thermr) , and pull up resistor (pad).

Thermistor circuits are far from accurate. They need calibration.
IMHO only good for crude thermostats.

One day you will discover the DS18B20.
Leo..

7

There is an online calculator ([SRS Thermistor Calculator](http://"http://www.thinksrs.com/downloads/programs/Therm Calc/NTCCalibrator/NTCcalculator.htm")) for the Steinhart-Hart coefficients that describe the Temperature-Resistance curve. You need to measure the resistance at three known temperatures and enter those pairs into the online calculator. With the coefficients you can calculate the temperature for any resistance.

This document describes how it all works:
[http://www.thinksrs.com/downloads/PDFs/ApplicationNotes/LDC%20Note%204%20NTC%20Calculator.pdf](http://"http://www.thinksrs.com/downloads/PDFs/ApplicationNotes/LDC Note 4 NTC Calculator.pdf")