First disclaimer - my reference device is a $30 crap thing from Amazon which uses type-K thermocouples. That said, checking with ice water and boiling distilled water the readings were where they should be.
I have three machines running Duet2 Wifi boards. I have been running cheap thermistors for the extruder temps, but I'm trying to get my machines more in sync - and extruder temps were not reading consistent across them so I changed one machine to a PT1000 from Slice to see if I can get readings to match my thermocouple thermometer. My machines are Raise3D N2-series printers and they have a long heat block. With the short Slice sensor I'm able to slide a 3mm diameter Type K probe well into the heat block and get a good temp measurements. I also tested with a bare TypeK junction shoved into the melted plastic in the hot end and that reads the same as the probe in the heat block, so I feel confident about my measurement technique.
I looked up the calibration processes. I have a 2000 (.01%) ohm resistor, which should compare to 266.4C on a PT1000. I also have an 1096 ohm array of resistors that should compare to 25C on a PT1000 and 1000 (.01%) resistor which should compare to 0C.
The semi-auto isn't an option on the Duet2 Wifi board. Tried the Manual calibration with resistors. That isn't calibrating the sensor, but the circuit. Are the PT1000 sensors supposed to be consistent enough that sensor-to-sensor differences can be disregarded?
If I put the 1096 ohm resistor on the E0 connector on the print head I get a reading of 25C with H15. With the 2000 ohm resistor I get 266.4 (or so) with L-2.
If I then hook up the PT1000 and set the heater temp for 270, the thermocouple reads 280. L-97 brings the PT1000 temp into line with the thermocouple. I then set the temp to 50C. With H127 the thermocouple reads 40C. I can't get an H value to make the PT1000 and thermocouple match.
The numbers I get with the resistor tests aren't correlating to an accurate temperature reading, and I have been unable to tweak the H and L numbers to get correlation to the thermocouple readings.
What am I doing wrong here?