Thermistors not recognized, open circuit temperature at 2000°C
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Hi @dc42 I have attached the config.g file as well as the images below showing that one PT1000 is hooked up to the Bed Thermmistor and the other one to the extruder is connected to E0 Thermistor 2.
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can you measure the resistance of your thermistors.
also post your config.g thermistor config. -
I have measured the resistance of the thermistors and its 1092 ohms.
I have measured across the two pins where the thermistors connect to the board and I get 4.68K ohms without the thermistors connected. I then did the same check with everything disconnected from the board and I still get 4.68k ohms.
Now with everything connected to the board including the thermistors I measured across the thermistor pins on the board and I get 0.835 and 0.837k ohms.
In my config.g file it says:[2_1561283639142_config.json](Uploading 0%) [1_1561283639142_config.g.bak](Uploading 0%) [0_1561283639141_config.g](Uploading 0%)
; Heaters
M307 H0 B0 S1.00 ; Disable bang-bang mode for the bed heater and set PWM limit
M305 P0 T362000 B26000 R4700 ; Set thermistor + ADC parameters for heater 0
M143 H0 S120 ; Set temperature limit for heater 0 to 120C
M305 P1 T110000 B3950 R4700 ; Set thermistor + ADC parameters for heater 1
M143 H1 S280 ; Set temperature limit for heater 1 to 280C -
R4700 is for the duet wifi not the maesto. the maestro uses R2200.
pt1000 are configured like this
M305 P1 X501 R2200 ; Configure PT1000 for heater 1
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I have changed the settings to
; Heaters
M307 H0 B0 S1.00 ; Disable bang-bang mode for the bed heater and set PWM limit
M305 P0 X500 R2200 ; Configure PT1000 for heater 0
M143 H0 S120 ; Set temperature limit for heater 0 to 120C
M305 P1 X501 R2200 ; Configure PT1000 for heater 1
M143 H1 S280 ; Set temperature limit for heater 1 to 280CBut still seem to be getting the same temperature readings.
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You can leave out the R parameter in the M305 commands because the firmware knows the correct value. It's only on really old boards (Duet 0.6 and Duet 0.8.5) that it is needed.
If the PT1000 sensors read 1092 ohms at room temperature. that is about right and you should get good readings from them.
Try sending M305 P0 with no other parameters, and check it reports that it is configured for a PT1000. Likewise M305 P1.
If that looks OK, try disconnecting both PT1000 sensors at the Duet and connect 1K resistors between the pins of the thermistor connectors. That should give you a reading close to 0C. if that works, then you may have a short between the PT1000 wiring and the heater wiring, perhaps via the hot end metalwork.
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also measure the resistance across R15, R19 and R53 on the board.
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So I have edited the config.g to state;
; Heaters
M307 H0 B0 S1.00 ; Disable bang-bang mode for the bed heater and set PWM limit
M305 P0 ; Configure PT1000 for heater 0
M143 H0 S120 ; Set temperature limit for heater 0 to 120C
M305 P1 ; Configure PT1000 for heater 1
M143 H1 S280 ; Set temperature limit for heater 1 to 280CUsing the G Code Console to send M305 P0 and M305 P1 to the machine and it replied with these settings
1:58:45 PMM305 P0
Heater 0 uses Thermistor sensor channel 0, T:362000.0 B:3950.0 C:0.00e+0 R:4700.0
1:58:18 PMM305 P1
Heater 1 uses Thermistor sensor channel 1, T:110000.0 B:3950.0 C:0.00e+0 R:4700.0
As I am only testing it and trying to get it ambient temperature the PT1000's are currently free in mid air in an attempt to prevent shorts against the metal work.
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that indicates that you are configuring your thermistors elsewhere.
check all files in the sys folder. especially config overwrite for any m305 commands.
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@Scally123, you misunderstood me. When I said:
@dc42 said in Thermistors not recognized, open circuit temperature at 2000°C:
Try sending M305 P0 with no other parameters, and check it reports that it is configured for a PT1000. Likewise M305 P1.
I meant you to leave the M305 commands in config.g alone, but to run those 2 commands from the console, to check that the 2 heaters were configured to use PT1000 sensors.
