PT100 - PT1000 Setup

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Resistance thermometers, also called resistance temperature detectors (RTDs), are sensors used to measure temperature. RTDs, which have higher accuracy and repeatability, allow for higher temperature print materials (up to 600C in some cases) and can be a very useful upgrade to your Jubilee build. The most commonly used RTDs in 3D printers are the PT100 and PT1000 series sensors, which require a little setup to work properly with a Duet controller. PT1000 sensors have only recently become more available to use, and are somewhat easier to configure since they can plug directly into your Duet controller board. PT100 sensors need an extra daughterboard to condition the signal and make it something readable by the microprocessor.

For a good comparison of the virtues of the common Temperature Sensors see the Duet Wiki page on Temperature_sensors. For additional information, please refer to the Duet3D wiki page for setting up RTDs.

PT100 Setup

To be able to use PT100 sensors on a Duet controller board, you will need to also install a PT100 daughter board to be able to accurately measure the signal from the RTD for the Duet controller.

Follows is a working setup using 2 PT100's on a Duet Wifi board running RRF3.1.1

; Heaters
M143 S300 ; Set maximum heater temperature to 300C
;M305 P0 X201 ; Set thermistor + ADC parameters for heater 0 and remap it to channel 201
;M305 P1 X200 ; Set thermistor + ADC parameters for heater 1 and remap it to channel 200
M308 S0 P"spi.cs2" Y"rtd-max31865" F50
M308 S1 P"spi.cs1" Y"rtd-max31865" F50
M950 H0 C"bedheat" T0
M950 H1 C"e0heat" T1
M140 H0                                 ; map heated bed to heater 0

The commented out M305's are for FW V2.x.x where the hottend is connected to the first port on the Daughter board if you want to contact a PT100 in the same order as normal then set P0 to X200 and P1 to X201.

PT1000 Setup

PT1000 sensors can be directly plugged into a Duet controller board without any additional hardware or electronics.

This is a working setup for 2 PT1000 sensors connected to the first 2 Thermistor inputs on a Duet3 running RRF3.1.1

; Heaters
M308 S0 P"temp0" Y"pt1000" R2200              ; configure sensor 0 as PT1000 on pin temp0
M950 H0 C"out0" T0                            ; create bed heater output on out0 and map it to sensor 0
M143 H0 S120                                  ; set temperature limit for heater 0 to 120C
M307 H0 B0 S1.00                              ; disable bang-bang mode for the bed heater and set PWM limit
M140 H0                                       ; map heated bed to heater 0
M308 S1 P"temp1" Y"pt1000" R2200              ; configure sensor 1 as PT1000 on pin temp1
M950 H1 C"out1" T1                            ; create nozzle heater output on out1 and map it to sensor 1
M143 H1 S280                                  ; set temperature limit for heater 1 to 280C
M307 H1 B0 S1.00                              ; disable bang-bang mode for heater  and set PWM limit

You may want to adjust the M143 line for your own usage case and the same will go for the I/P O/P Pins.

How to determine wiring issues

RTD's (aka PT100/PT1000) are Positive Resistance Temperature devices meaning that their resistance increases with Temperature (opposite of a NTC Thermistor) so a High resistance joint will show higher temperatures whilst a short will give you a zero or very low reading.

Also note that the Meastro and Duet3 have the Thermistor inputs optimised to cope with PT1000's much better than a Duet WiFi/Ethernet due to them using a 2.2K sense resistor instead of the 4.7K one (all future boards are likely to have the 2.2 one by default)