I spent the better half of the day trying to debug the 3040 - I returned to an old working hardware setup with some extra 100 Ohm platinum RTDs, but I couldn't get one of the 3040's to read it in the right way. Resistance is "err", and nothing I seem to do or plug in seems to change it.
- I checked the cabling to the 3040 - it was fine (no open connections, or mysterious shorts)
- I checked the software limits and tried to make them as large as possible
- I checked the sensor type and its coefficients
- I switched the RTDs between 3040's, the failure followed the 3040
- I did the onboard calibration for the RTD with a 100 Ohm thin film, as per the manuals instructions
- I calibrated out the RTDs leads with a short, as per the manuals instructions.
- I restored the machine to an earlier state (presumably from when it was still @ MIT), and repeated the above - still nothing.
Back story which may or may not be pertinent (guesses at possible damage here).
- I snapped off the lead from my 100 Ohm RTD on my oven a few days ago.
- I tried to use a 1000 kOhm RTD which I already had affixed to the oven as a spare, but the 3040 doesn't seem to know about these -
- I had a 1 kOhm RTD in with the coefficients from a 100 Ohm for a bit (as it wouldn't let me switch them)
- It seems unlikely that the having wrong sensor type could damage your 3040, as you have to cycle through types with the ipod-esque wheel to select the right one.
I then tried to use an NTC thermistor as the sensor, since I had some already wired up.
- The manual quoted +/- ranges for the Steinhart-Hart coefficients for thermistors, which seems to imply that NTC and PTC are O.K to use
- I pulled the NTC Steinhart-Hart coefficients from a quick matlab fit
- When I tried to use them,the 3040 told me they were illegal and forced the coefficients back to their default positive values
I abandoned this and soldered some connectors on some spare 100 Ohm RTDs, of the exact same type which is working on the other 3040. I then experienced the problems from the first list...
I hope there is something stupid that I am somehow missing, otherwise I either have to skip the last couple measurements for the paper, or wait wait wait for a replacement / refurb / homestyle debugging of the 3040 - I will try to recruit a fresh set of eyes tomorrow to look at this.
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