Extremely wrong temperature reading on thermocouples

  • Hello. Somehow I’m getting very wrong temperature readings on my thermocouples when I’m trying to tune my E3D V6 hot end. I have been able to do few successful prints after I get everything up and running but now something strange happening. I get my thermocouple reading at 150 C when my hotend reaching 206 C. This is happening with both 30W and 40W E3D heaters. I run PID autotune few times and it didn’t help at all my reading just getting worse. I wanted to make sure if it absolutely necessary to isolate thermocouple from hot end? I did not do that on my old setup and I can run 5 hours print without problem. I don’t have any high temp tubing at the moment so I used capton tape for isolation if thermocouple. My question is what go wrong with my current setup? Is this PID error or my thermocouple is failing? I’m a bit puzzled what go wrong and would be grateful for advice what to do in this situation.
    This is my config.g settings regarding thermocouples for 30W E3D heater.

    M305 P1 X100
    M307 H1 A167.5 C184.7 D9.5 B0

  • administrators

    If you don't isolate the thermocouple from the heater block then it is likely to pick up noise. Also, heater cartridges occasionally fail with a short between the element and the heater block, so unless you isolate the thermocouple you risk getting a short between the heater voltage and the thermocouple input.

    I recommend that you get the E3D cartridge thermocouple and compatible heater block, then you can be sure of isolation and good thermal contact. You may wish to buy the E3D silicone sleeve at the same time.

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