I'm having real difficulties here. I'm a complete electronics novice trying to use a TMP1200 + RTD Probes + HUB0000 to measure temperatures on my coffee roasters. The probes were recently calibrated, so I'm as confident as I can be that they're ok.
I've followed the instructions on the Phidgets user guide. Somehow, after wiring up the same RTD probe (3-wire) to two different TMP1200 sensors (because it's a duplex RTD probe) I'm getting two different resistance measurements and therefore two different temperatures (9 degs c and 20 degs c). It's the exact same probe that's being read from. Also, the temperature reading is off by about 5 degrees celsius at ambient temperature.
The only variable, as best I can tell, is the short wire between EXC+ and RTD+: I'm used some wire which is different (in terms of material) to the wire used by the RTD probes themselves. The short wire on one of the TMP1200 is longer than on the other. However, I've been trimming down the longer one and it has made zero difference.
I'm at a complete loss. The probes and sensors are useless to me in their current state. Can somebody please help?