NTC Glass enclosure Thermistor strange output

Other Hardware Sensors
1

Hi there,

Im using glass NTC thermistor 10k Ohms for a digital thermometer with arduino S3V.3 R2 and the code i use is Temperature Measurement using Arduino and a Thermistor | Beyond the Standard Model Pub
but the ouput i get is like this " V=3.43V R_th = 21037.89Ohm T=8.85C " and the room temp is actually 25-26 deg.C. The thermistor I use DKA-103 datasheet http://docs-europe.electrocomponents.com/webdocs/002a/0900766b8002a59e.pdf
i found some also T/R data Josephrinek.com
form page 10 are the 10k ohms thermistors. I cant understand whats wrong. I also tried this Arduino Thermistor Tutorial and the temp i get ont the screen was around 43 deg.C. I think its sth wrong with Steinhart-a,b,c const...but nothing fixes it. Any ideas why ?

2

Are you using a 10K series resistor with your thermistor? A schematic diagram or a photograph of your circuit would be helpful.

3

Well i dont have camera to make photo.And Im using this diagram (+5V) —- R=10k —-analogpin0 —- Thermistor 10k — GND

4

chelev:
Well i dont have camera to make photo.And Im using this diagram (+5V) —- R=10k —-analogpin0 —- Thermistor 10k — GND

Is your Arduino a 5V or a 3V3 model? The resistance you are calculating for the thermistor implies that it is not a 10K thermistor or you are not powering it with 5V or something else that mimics those symptoms. For example, if you are using a 3V3 Arduino and powering the thermistor off 5V, the results you are getting would imply a temperature of around 26 deg.C.

5

Hmm.. The volage my arduino is running is exacly 5.04V after the volatge regulator and the thermistor is specified to be 10k. I really dont get it :roll_eyes:

6

Can you measure the thermistor resistance at your ambient temperature with a multimeter?

7

Actully i heva done this earlier and at 26 deg.C i measured 9k and sth i dont remember it. but now as im looking my board i found one interuped line which im going to solder right now its cutting the line GND line between C5 and the other components afre it meaning C7, C8 and pin 23 of the ATmega i everithing will be ok with the ATmega..i will feed u on the work progress after a few mins. Thanks for helping.