PT1000 thermistor configuration
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@Arminas The temperature circuit is a voltage divider with inline resistors, so yes, you should read some resistance. It looks like you're measuring across the temp sensor pins with the PT1000 still connected. In which case you're measuring about 1100 ohms in parallel with about 2K to 3K. So 774 ohms is believable. I just measured a bare 1LC board, and get 2.7k ohms on temp0 and temp1. See the schematic here: https://github.com/Duet3D/Duet3-Toolboard-1LC/blob/master/Toolboard_1LC_v1.3/Duet3_TB_1LC_Schematic_v1.3.pdf
Ian
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@droftarts Could you please explain a little more about this test - how do I differ if it's board or wiring? Maybe I can measure resistance of temp sensor pins on the board?
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@Arminas said in PT1000 thermistor configuration:
Could you please explain a little more about this test
- Turn off power, disconnect the PT1000 from the 1LC
- Measure the resistance on the wires to the PT1000. You have already done this, resistance was 1102 ohms.
- Measure the resistance across the temp0 pins of the 1LC, without the PT1000 connected. It should be around 2.7k ohms. Measure the temp1 pins as well.
Generally, in order of most likely to least likely, spiky temperature readings are caused by:
- intermittent wiring - loose connections, poor crimping, frayed wires, dry solder joints. It may only happen when the wiring moves, or when temperature changes.
- failing temperature sensor - may only show when at temperature
- Electrical interference - usually from heater or motor wiring running very close to the temperature sensor wiring. Generally shows when machine is operating
- Power supply issues - faulty or failing power supply, external power spikes (eg large/noisy dc motor on the same electrical circuit starting/stopping)
- Hardware issues - faulty Duet board. Try connecting the PT1000 to the other temperature input on the 1LC, or move the temperature sensor and heater to the mainboard to test
- Firmware bug - least likely because this is heavily tested, and would be reported by other users.
Ian
