I have put together a remote temperature sensor using the Thermistor tutorial located at, http://devwiki.electricimp.com/doku.php?id=thermistor:advancedntc.
Instead of a 10k thermistor I got a 100k from Digikey (http://www.digikey.com/product-search/en?vendor=0&keywords=495-2143-ND), THERMISTOR NTC 100K OHM 1% RAD, part #B57861S0104F040.
In the code below:
// calculate the resistance of the thermistor at the current temperature local r_therm = <u>100000.0 </u>/ ( (v_high / v_therm) - 1); local ln_therm = math.log(<u>100000.0</u> / r_therm); local t_therm = (t0_therm * b_therm) / (b_therm - t0_therm * ln_therm) - 273.15;
I changed the 10,000 to 100,000 to compensate for the 100k thermistor and I also changed the b_therm from 3988 to 4540 for the same reasons.
I have the impee up and running however the reading’s are about 5 degrees higher than my other thermometers.
When I change the ‘1’ in the code below:
local r_therm = <u>100000.0 </u>/ ( (v_high / v_therm) - 1);
to a ‘2’. My readings are closer to what the thermometers are reading.
So my questions are:
Is it correct to alter the code to compensate for the differing (10k to 100k) thermistors?
In the code, where I changed the ‘-1’ to a ‘-2’, was is this ‘1’ for?
And lastly, please help, any suggestions are welcome!?
Thanks in advance for all responses!