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# Help needed with NTC resistance calculation

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#### JunglePython

##### Member
I have a 100k NTC.

I want to be able to calculate its resistance at various temps.

Information supplied with the NTC gives me the following Formula:

R = Ae^B/T

R = the thermistor resistance in Ohms.
T = temperature in Kelvin.
e = natural logarithm base(2.718).
A = approx. 0.0277.
B = 4400

It has been a long time since I used my calculator and I cant get this to work.

Could someone please explain how to use this formula on a calculator.

For the purpose of the explanation could you calculate the resistance at 25 degrees celcius.

Cheers

Luke

If you have BASIC on your computer, write this program:

5 INPUT"DEGREES C=;C
10 A=.0277
20 B=4400
30 T=273+C
40 E=2.71828
50 R=A*E^(B/T)
60 PRINT "R= ";R
70 END

I have run the program for these temperatures:
25 deg r=71594
50 deg r=22832.9
75 deg r=8581.3
100 deg r=3677.2

Hi

Thanks for the reply. I think there is something wrong with my formula.
The formula and values I posted were for a 100k @25C NTC.

When I worked it out on my calculator I got 71k just like you did.
This should be 100k. This is why I was questioning myself about my calcuator skills.

Cheers

Luke

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