Temperature sensors

The Duet series supports 4 types of temperature sensor: thermistor and PT1000, thermocouple, and PT100.

Here are the pros and cons of each:

Property	Thermistor	Thermocouple	PT100	PT1000
Cost	Low	Medium	Higher	Higher
Precision	Low	Medium	High	Medium
Needs adapter board?	No	Yes	Yes	No
Susceptible to interference?	No	Very	Somewhat	No
Temperature limit	Typically 280-300C	Up to 1100C depending on type	Up to 500C depending on type	Up to 500C depending on type
Special considerations	Because thermistors are not very accurate, if you replace the thermistor or the electronics then the readings may change by several degC. So you may have to re-learn what temperature indications give you good prints.	To get accurate cold junction compensation, you need to run the twisted pair thermocouple leads all the way from the hot end to the adapter board. So you can't easily include the thermistor connections in a connector for a demountable hot end.	For best accuracy, use a 4-wire connection	Lower resolution than other sensors. If you use PT1000 sensors with the Duet 06 or 085 then you will probably need to calibrate the ADC by substituting fixed resistors for the PT1000 and adjusting the H and L values in the M305 command to get accurate readings. A 1K 1% resistor should give a reading of 0C +/- 2.5C and a 2K 1% resistor should read 266.5C +/- 5C.

A thermistor is adequate for monitoring bed or chamber temperature
If you have only one printer and one hot end, a thermistor is normally adequate for the hot end
If it is important to you that multiple identical printers or multiple hot ends need the same indicated temperatures to provide identical performance, use PT100 or PT1000 sensors
For temperatures above 300C, use PT100 or PT1000 sensors
For very high temperatures, use thermocouples
PT1000 sensors are potentially a good cost and performance compromise between thermistors and PT100 sensors. The thermistor inputs on the Duet 2 Maestro and Duet 3 are optimised to work well with PT1000 sensors.

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