thermometer probe question.

[Geoff]

ok, i want to fake out a thermometer probe. this is the one on the A/C chiller i am making. the A/C unit has a thermometer that turns off when the temp reaches 64 degrees. that is not low enough for me. i would like to fake out the thermometer so it is reading higher than it actually is. i figured it is based on resistance in the probe, but i do not have an idea on how to figure out what kind of resister to put in line with it to think that it is lets 30 degrees warmer than it actually is.

any of you all know what i should test or try to figure this out.

apparantly different probes have different values. this is just a FYI. if i put the A/C probe on the RS thermometer i got a reading of 120 degrees when the RS probe read 74. the resistor still seemed to behave the same for both though.

G~

[Geoff]

Ok, this is what to do. i am dangerous if i have what i think i need.

anyway this is real easy. i had a dumb Radio Shack $10 thermometer that i use for the chiller bath, so i know what is going on down there. this was my guinea pig. i had a bunch of resistors lying around so off i went expermimenting. this is pretty fun by the way. if you put the resistor in series with the probe the temp will appear to go down to the thermometer. if you put the resistor in parrallel the temp will go up. super simple and cool. i think i used a 50k resistor to get about 23 degree offset.

this worked out perfectly. the A/C unit i had a thermostat, so now i can adjust the temp of the chiller water bath depending on what is needed.

G~