HeaterMeter 4.3 Thermocouple Troubleshooting.

[Brad-Skittletop]

Finished building my HeaterMeter 4.3 with thermocouple and went surprisingly well. Booted first time, accessible on my network, blower and servo both working. thermistor probes 1-3 all working.

My problem is probe 0, the thermocouple does not appear to be working. It starts as a really high number and counts down to 32F. (with or without the thermistor probe plugged in, also shorting the two inputs has no effect) I ensured it's set to thermocouple in the web UI configuration tab. Probe 0 diagnostic shows:
P0 ADB00000 00Nz
Kcouple 32.00 F

Does anyone have any suggestions on where I could start troubleshooting?

Thanks,
Brad.

 

[Bryan Mayland]

What that diagnostic message from the LCD is saying is that the Pit input into the ATmega is grounded (reading 00000). If it starts high then slowly drops, that's weird, I'm not sure what would cause that behavior unless the AD8495 chip is being overtaxed somehow and stops outputting current to the probe (and therefore it will drop to 0V).

I'm not sure to tell you where to look to troubleshoot that, maybe start with checking the output from the AD8495 (the big giant hole to the bottom left of the chip is the easiest place to get this) to ground and making sure it isn't shorted? Also check from the TC+ and TC- pins to ground and look for about 1k there.