Thermocouple daughterboard "sensor short to other wiring"



  • Hi there,
    I have had a Duet3D Wifi 2 with a J type thermocouple, and all was working fine until doing maintenance work on part of the printer. One of the terminal blocks was damaged by the thermocouple cable being pulled, so I switched to using the second thermocouple channel (T1).

    I changed config to use M308 P1 X151, but I am getting a "sensor short to other wiring" error.
    Steps to solve issue:

    1. Tried switching the cables (in case the red/blue colour coding was US instead of Dutch/German)
    2. Tried inserting a 330 Ohm resistor instead of the thermocouple. The Duet gave a reasonable temperature reading of 25 C.
    3. Checked the thermocouple wires at the hotend side and moved the metal shielding up so it wasn't touching the heating block.

    Also, I don't know if I am just being thrown by the phrasing of the error message, but if the terminal is empty the Duet thinks there is a sensor short.

    Any suggestions?


  • Moderator

    @qubit said in Thermocouple daughterboard "sensor short to other wiring":

    Tried inserting a 330 Ohm resistor instead of the thermocouple. The Duet gave a reasonable temperature reading of 25 C.

    In that case I'd expect the problem to be in the wiring, not with the thermocouple board or config. How did the cable get pulled? I'd expect that it is broken, or has increased resistance, somewhere along it's length, which will throw the reading out and cause the error message.

    Ian



  • Thanks @droftarts, you may be right that it could be a wiring issue. The thermocouple is bare and I don't have any kapton tape at the heat block. Funnily though it is working, sometimes. The thermocouple reads 2000*C if it is touching the heat block when the Duet starts, but if I start the Duet and then insert the thermocouple it works fine (even after using the emergency stop).

    I wasn't using insulation (e.g. kapton) before but it was working without having to do this cheeky tricky. Maybe I got lucky and there was enough dirt/resistance? Are there any alternatives to kapton tape?


Log in to reply