Rctime and ntc

[larosacristian]

thanks again, that you say, 367x100 = 36700/4.7 = 7808/100 = 78 but I have to get 6 ° C not 78 what is wrong?

[Archangel]

You know what? It's not going to be linear anyway, so don't lose too much sleep over it.
“Steinhart-Hart” is something to google, it looks like thermistors make a big "S" curve on a graph.
Here is a link to thermocouple chart for the common K type thermocouple, see if you can find something similar for your particular thermistor
so you do not have to make your own.
BTW what are you making here anyway, and how critical are the readings ?

Check these 2 threads:
http://www.picbasic.co.uk/forum/showthread.php?t=14216
http://www.picbasic.co.uk/forum/showthread.php?t=14008

[aratti]

NTC are negative termoresistor. Which means that while temperature increases resistance of the termistor decrease, so they are inversely proportional.

Al.

[Archangel]

RE: Yes it does but it does not mean they are linear, which is why I do not think simple division will have accuracy.

[larosacristian]

thanks for the answers, I do not need to be precise I just have to control the switching on and off at a given temperature a fan then, that there is an error of a degree I do not care.

[AvionicsMaster1]

Of the one specific thermistor I looked I downloaded the excel file and from 0 degree to 100 degree the curve is indeed exponential. I tried to import the data into excel but I've forgotten how to get it to give you a formula to fit the data entered. I browsed a few others and they all look about the same but you can find the math for a precise formula at http://www.epcos.com/web/generator/W...dardizedRT.pdf. Putting that into PBP will be a challenge to say the least.

This site though has a much easier formula if you know a little of your thermistors' data:http://www.mstarlabs.com/sensors/the...libration.html

Though I thought this site gave you a better idea of how to find the right formula:http://www.cantherm.com/products/the...osing_ntc.html

[larosacristian]

thank you very much I will try to set formulas in pbp and let you know. thank you very much. if someone already has some sample code that can assist me I would be most grateful if you would provide me. greetings