Temperature readings are wrong



  • Hello All,

    I cannot get the Duet Maestro to read the temperature correctly. I am trying to use PT1000’s for the bed and hot end however I get temperature readings of 207.7ₒc for the Bed and 147.2ₒc for the hot end, when both are at 22ₒc. The PT1000’s are dangling in fresh air and not touching anything as to prevent any possible leakage.

    I have used resistors across the bed thermistor pins and extruder thermistor pins in order to create resistances that tally to specific temperatures as stated in the chart below.

    0_1562961315207_Capture.PNG

    I connected 1K, 1.2K, 1.3K and 1.5K resistors which should’ve returned values of 0ₒc, 52ₒc, 78ₒc and 130ₒc. I had attached them using a connector strip and had them dangling in fresh air and not touching anything as to prevent any possible leakages or shorts that could give false readings.

    After connecting the resistors across the pins for the Bed thermistor and the Hot end Thermistor and the power turned off I checked the resistance across these connections and the resulting resistances are displayed in the table below. I then powered up the board and got the simulated temperatures from the web interface and have listed them in the table below.

    0_1562961305642_Capture1.PNG

    Have I set something wrong in my config? When using the RRC it automatically puts in the PT1000 information. What is going wrong?

    Here is my config.g 0_1562961462144_config (3).g

    I have had similar issues before which I have linked to the previous post here.



  • Your config.g is wrong. You have:

    M305 P0 ; Configure PT1000 for heater 0
    M305 P1 ; Configure PT1000 for heater 1

    A cursory review of the documentation shows you need more parameters than that.

    Recommend reading:

    https://duet3d.dozuki.com/Wiki/Connecting_thermistors_or_PT1000_temperature_sensors
    https://duet3d.dozuki.com/Wiki/Gcode#Section_M305_Set_temperature_sensor_parameters


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