July 2014: BenchBuddEE

July 16, 2014

I wanted to see if the thermocouple circuit would actually work with a, you know, thermocouple, so I took the Type K probe that i had laying around from some previous DMM that I blew the hell out of, and connected it to TC_IN+/- with alligator clips and turned the benchbuddy on. No luck. Then I remembered WHY we have the instrumentation amp there in the first place and put the gain jumper on… I got a semi-stable value with the 10Ω resistor setting. My DMM showed 0.4mV (teeeeeny signal) at the CH0 test point.

This is a copy of the build log I maintained during the Contextual Electronics Session 1B class. I didn’t log the steps taken during the circuit design and layout portion, but since most of that was rip-up, re-drawing and time spent searching Digi-Key, you’re not missing much, I promise.

I held the tip of my soldering iron to it and the value jumped significantly, then after taking the tip away, it slowly came back down to 0.4mV again. I suppose the idea now would be to do some math in code to compare that against the cold junction value to come up with an actual temperature!

Very cool!