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Original post by: Curtis Heisey ,


I got the E3D Pt100 temp sensor and amp working with my Prusa MK3, but it took some doing to install and debug it. I had to piece together a number of disparate pieces of information. Some tips.

0) Check wiring and make sure you are getting +5 on the board.  Make sure FW build is modified for sensor and sensor signal is going into pin that FW is expecting. Sounds like you did all this. Not trying to insult your intelligence.

1) PT100 sensor.  First check the unattached PT100 sensor. It should be about 100 ohms at room temp.   There is a nice blog on how these sensors work (the “PT100” is an industry standard). About 3/4 down the way on the blog there is a figure of sensor resistance vs temp. Check several temps. Then you can determine if the sensor is faulty or not.

2) Installation. Be careful of tightening the PT100 cartridge too much. Turn screw to touch sensor, than additional 1/8 turn, NO  MORE. The cartridge is easily crushed/damaged.

3) Open leads.  If your temp reads the max range and does not vary, you have likely have an open circuit between the sensor and the amp, or the PT100 cartridge

4) After item (1) is good, check amplifier signal out.  On the wiki [[E3D PT100 Amplifier Documentation]] there is a table of amplifier voltage out vs temperature “Output Characteristics”

Hope this helps.

I had mine working for awhile, then one of the leads broke loose. Read 999C. Installed a new one and it now seems to be reading a constant 70C too high, so I am back to step (1) above to try to determine if the amp or sensor.