R type thermocouple reading incorrect
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Hey guys,
Long time lurker, first time poster.
Wonder if you can help me out. I am using an R-type thermocouple on a project that I'm controlling with a duet 3 and associated thermocouple daughter board. And yes, I'm using temperatures that need an R type thermocouple.
Anyway, the issue I am having is that i'm not getting a right reading from the thermocouple. I have a flir high temperature camera to take direct readings. The thermocouple seems to be out by a factor of around 4. So if the duet interface is telling me that the temperature is 200C then it's actually 800C give or take. Obviously this is a bit of an issue so I was wondering if anyone had any pointers?
The thermocouple is a ceramic tube type thermocouple that has a terminal block at the end. From here I have around 4ft of compensated wire to the daughter board. The thermocouple is 290mm long. I have set the thermocouple as a type R in the config file.
I had considered moving the daughter board to the rear of the thermocouple but would an extension wire between it and the duet 3 board cause any issues or work at all? Is there something else I'm missing?
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@gary-0 is the polarity correct? Black is +
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@3dpmicro yes the polarity is correct
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@gary-0 post your config.g file
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@gary-0 Is the daughter board the later version which uses the MAX31856 chip? I ask because the earlier version daughter boards used the MAX31855 which only support type K thermocouples.
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@dougal1957 You lovely lovely person.
Asking me to post it made me go back through it with the appropriate paperwork in hand to check everything over before sending it through. And I spotted a rather obvious error, essentially trying to define the thermocouple type using the wrong variable.
Thanks for all your help folks. So handy to be able to bounce things off others in the know!
