3d printing review

High temperature PT100 probe

If you bought a budget printer or hotend most probably it was designed for up to 240 – 260°C. This is a perfectly fine temperature for PLA, PETG, and ABS. If you want to print Nylon, PC-ABS, PC, Carbon composites, and other exotic filaments though, you need to upgrade your setup for higher temperatures (270-350+°C). One of the upgrades is installing and configuring a high-temperature probe. This article is reviewing the PT100 sensor.

PT100 sensor – advantages for 3d printing

  • Enables high temperature and high accuracy readings up to 450°C. It is perfect for 3d printing, because of its excellent stability and repeatability. It could even be used in the range of 450-500°C with small fluctuations.
  • More precise than a thermistor
  • Mature and reliable technology
  • Well-documented for most firmware (Marlin, Klipper, etc.)

PT100 is not a thermistor – you may need an amplifier

The PT100 is not a thermistor. It is an RTD (Resistance Temperature Detector) device. The output from PT100 probes is not supported by most budget control boards by default. It requires a separate converter (amplifier board) to translate the PT100 signal to 0-5V analog signal.

Unless your control board explicitly supports RTD probes you will need an additional amplifier board. Ultimaker 2 and up uses PT100 sensors by default, so no alteration to the electronics or firmware is needed. Most aftermarket control boards need an amplifier board. Some high-end boards like the Octopus I have on my Voron Trident support PT100 sensors.

PT100 – connect an amplifier board

There are 2 ways of connecting a PT100 amplifier board to your control board and 2 types of amplifiers. Let’s call them “traditional” and “easy”.

The “traditional” amplifier requires a free analog input on your board (check the PCB diagram of your boards for pins that start with a capital A (normally on headers labeled AUX or EXP)). The wiring consists in:

  • Powering the amplifier board (0v and 5v pins) from your controller or external power supply.
  • Connecting the signal output pin to an analog input
  • Connecting the probe to the amplifier
PT100 traditional amplifier board for 3d printing
2-wire PT100 and amplifier board are largely available on Amazon and Aliexpress

The “easy” amplifier requires a free stepper driver socket. The connection is super easy – just plug the amplifier in the stepper driver socket and connect 4 wires PT100 in the stepper motor connector.

MAX31865 PT100 amplifier for stepper driver socket
This amplifier board is well specified in the BIQU documentation. Its easy and error-free connection makes it a better choice if you have a spare driver socket on your controller. It supports also 2,3 and 4 wires PT100 and PT1000 probes through a selector switch. Available at Aliexpress.

PT100 – alternatives

There is a number of other probes and high-temperature thermistors to enable high-temperature printing. Examples are PT1000, K, or D-type thermistors. Their advantage is they don’t need an amplifier. The huge minus though is they are less accurate than PT100.

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