I have the following datasheet for a thermisistor: http://make-documents.s3.amazonaws.com/UGulDNLaIajWgPom.pdf

I am trying to use the formula (found here http:// iwantmyreal.name/blog/2012/09/23/measuring-the-temperature-with-an-arduino-and-a-thermistor/): $$ 1/T=1/T_0+1/B*ln(R/R_0) $$ I am not sure I'm using the correct values, my understanding is that the values provided in the datasheet are as follow: $$R_0=20,000 ohm,$$ $$T_0=25 C,$$ $$Beta=4300$$ Can anyone confirm that this is correct?

I'm trying to get a temperature reading out of that sensor using an Arduino UNO microcontroller using the following found at http://playground.arduino.cc//ComponentLib/Thermistor2 at the bottom where it says example #2 using numbers instead of episco k164 definition .... (substituting with the above values)

The results are ~41.96 degrees F, and the room is between 75-80 degrees F so that means the temperatures readings are way off, I don't understand why unless I got the wrong values from the datasheet. Also I have two of these sensors and both give about the same value.

Code currently using:

// Code obtained from http://playground.arduino.cc//ComponentLib/Thermistor2
#include <math.h>
// enumarating 3 major temperature scales
enum {

// manufacturer data for episco k164 10k thermistor
// simply delete this if you don't need it
// or use this idea to define your own thermistors
#define EPISCO_K164_10k 4300.0f,298.15f,10000.0f  // B,T0,R0

// Temperature function outputs float , the actual 
// temperature
// Temperature function inputs
// 1.AnalogInputNumber - analog input to read from 
// 2.OuputUnit - output in celsius, kelvin or fahrenheit
// 3.Thermistor B parameter - found in datasheet 
// 4.Manufacturer T0 parameter - found in datasheet (kelvin)
// 5. Manufacturer R0 parameter - found in datasheet (ohms)
// 6. Your balance resistor resistance in ohms  

float Temperature(int AnalogInputNumber,int OutputUnit,float B,float T0,float R0,float     R_Balance)
  float R,T;


  switch(OutputUnit) {
    case T_CELSIUS :
    case T_FAHRENHEIT :

  return T;

void setup() {

void loop() {

 Serial.println("10k Balance");

  • \$\begingroup\$ Do you have a schematic/code? What value resistor are you using for the balance resistor? \$\endgroup\$
    – Oli Glaser
    Aug 28, 2013 at 4:58
  • \$\begingroup\$ Sure. If you look at "Thermistor Test Schematic" Under playground.arduino.cc//ComponentLib/Thermistor2 that's pretty much it, except I'm using a 9.77 Kohm resistor (I measured it with a Voltmeter). Or +5V --> thermistor <-- Node 1 --> 9.77kohm --> ground. Then I have a connection from Node 1 to port A0 of the arduino uno microcontroller. I hope it makes sense, let me know if it doesn't. \$\endgroup\$
    – joze
    Aug 28, 2013 at 5:34
  • \$\begingroup\$ That's a start, thanks (it's usually a good idea to include the schematic and any code for your setup, so everyone knows exactly what you are doing) What is the exact code you are using? \$\endgroup\$
    – Oli Glaser
    Aug 28, 2013 at 6:14
  • \$\begingroup\$ Thanks for the tip, will do for next time. The code is the following: \$\endgroup\$
    – joze
    Aug 28, 2013 at 6:24
  • \$\begingroup\$ See above in the original question for my exact code, site won't let me edit my last comment. \$\endgroup\$
    – joze
    Aug 28, 2013 at 6:31

1 Answer 1


For anyone interested in knowing how I solved this problem, I used the AREF and 3.3V from the Arduino microcontroller connected directly one of sides of the thermistors. I believe the voltage coming out of my laptop was dropping; USB +5V was dropping to ~4.7V thus making my calculations lower.

Here's the website which helped to find my answer (this site includes CODE and DIAGRAM):


Thanks everyone for your help.


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