Which EPCOS 100K thermistor



  • I like many other hobbyists I am sure have received EPCOS 100K thermistors for their build.

    I have selected some values found on the forum here but after testing with my infrared thermometer, it’s about 10degC off (actual temp is less).

    My thermistor didn’t come with a marking or data sheet. How do I know which one I have so I can go look for the data sheet?

    Thanks in advance!


  • administrators

    Can you ask the company you bought it from what part number it is?

    is it 10C off at low or high temperatures? How did you measure the actual temperature?



  • @chanders testing hotend with IR thermometer is not at all a reliable way to do this. IR thermometers are crazy inaccurate on metallic surfaces and also surface temperature itself is different from inner temp.



  • how do i measure the temperature than ? i tried laser device, but it does not seem to be very accurate too...



  • @dc42 said in Which EPCOS 100K thermistor:

    Can you ask the company you bought it from what part number it is?

    I can ask but it was from one of the generic Chinese vendors on Aliexpress

    @vlad said in Which EPCOS 100K thermistor:

    @chanders testing hotend with IR thermometer is not at all a reliable way to do this. IR thermometers are crazy inaccurate on metallic surfaces and also surface temperature itself is different from inner temp.

    I was measuring the hotbed directly on the trace (coated side). I didn't realize IR thermometers were so inaccurate. The documentation siat the accuracy was +/- 1degC


  • administrators

    If it's a generic Chinese bed thermistor then those are usually 100K @ 25C with a B value around 3950.

    IR thermometers are useless for measuring hot end temperature, but can give a reasonable indication of bed temperature. If you have glass on top of the bed heater than there will be a temperature drop of around 5C across the glass @ 65C and 10C @ 100C.



  • One way to make IR thermometers a bit more accurate for shiny surfaces is to use a piece of black tape to use as a measuring point. Not exactly feasible for the hotend or other high temp surfaces. But it does work quite well on my shiny aluminum bed. I've also heard of people using black marker, but haven't tried it myself.



  • @phaedrux it's still a gamble. No guarantee it will be accurate. IR beam is also quite large and hotend is small. In order for IR to measure temperature, the surface has to fill the beam completely. For hotbed also it is easy to just use contact thermometer, will be much more reliable.


 

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