Thermistor help with ASD1115

Hardware
1

hi yall!

i just resumed my project that involves mycodo. I’m trying to use a NTC 3950 100k thermistor connected to a ASD1115. the ASD1115 input is successfully giving me a voltage, but i cant seem to get the calibration right.

here is my current config:
unscaled min: 0
unscaled max: 3.3 (my thermistor is running 3.3v)
rescale method: linear
rescaled unit min: -50
rescaled unit max: 300 (min and max from here)
Rescaled Measurement: temp, C

my readings which should be around 25c are at 14c. does anyone have any suggestions on how to fix this? I’m worried that its proportionally wrong, not just an incorrect offset temp. maybe an equation scale rather than a linear?

also, I wanted to say thank you to Kyle for this tool!

2

Hi Coby,
What does the datasheet specify for the tempterature curve?

3

im pretty new with thermistors and ADCs, this should be the datasheet but I’m not sure what I’m looking for

4

Are you using a voltage divider in front of your thermistor?
You can’t just connect the thermistor directly to the ADC.
You need something that looks like this…
image

5

Your datasheet indicated your temeprature curve is not linear. Here is a good resource detailing several measurement caluclation methods.

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6

yes, I’m pretty sure I have a voltage divider with a 100k resistor

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