The two EGT inputs worked fine last year with
- older firmware (1.0.18 or 1.0.19)
- the board is version 3.2
- AREF mod (just a short)
- MegaTune 2.25 (used now and before)
But don't seem to work after a firmware upgrade to 1.0.38. The symptom is that when a thermocouple is connected the temperature in MegaTune will display 0 with short spikes to what seems to multiples of 64 degrees at random intervals, about 1-2 times every second (this happens with nothing connected too). But... - If I put the thermocouple under a flame the temperature will stop fluttering and remain at 0.
The input on the MCP3208 measures analog voltages that are appropriate for the ambient temperature. Using the same thermocouple (measuring ambient temperature I get):
At the AD597 outputs
- 0.29 V for EGT1 (top chip)
- 0.19 V for EGT2 (bottom chip)
At the MCP3208 :
- 0.115 V on MCP3208_CH5 (EGT1)
- 0.082 V on MCP3208_CH4 (EGT2)
The measured voltages react in the expected way when the thermocouple is put under the flame (1.5 Volt ++), but this seems to be ignored: either the wrong channel is being read, or MegaTune is looking at the wrong values.
- manually test: with terminalprogram view-hex mode, (Manbyebye so it is not manual-command mode but megatune binary mode) "AAA", and look at offset 24,25 and 26,27 of the A command's reply (neglect the first reading)
The board currently runs 1.0.36 and I will upgrade to 1.0.73 in the coming days in hope that I can get it working again. Anyone else have an answer to why it stopped working with just a firmware upgrade? I will try the manual test described above if the firmware upgrade doesn't solve it
I am having this exact same problem too - initially I thought it was a grouding issue because there were a few problems with the way the block was grounded. Everything works fine except for the spiking values of the EGT - exactly as you describe. /(/PhatBob)?