Termistor headache
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Thanks.
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@ziggymanpopo thermistors and PT1000 connect directly to Duet, see https://duet3d.dozuki.com/Wiki/Connecting_thermistors_or_PT1000_temperature_sensors
PT100 (and thermocouples) need extra board see https://duet3d.dozuki.com/Wiki/Connecting_PT100_temperature_sensorsIan
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So no pt 100 without a daughter board is what i got out of all this the tesistance would be to low and read shorted hence froth a fault
But the pt 1000 can be directly attached
Is the inline resistor fixed on the duet wifi2 -
The links helps to understand
Thanks ian -
@ziggymanpopo Just to make sure... what meter You use and on which measurement range ?
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What the limit of the device was i asumed the two were of diferant uses the tp100 being toped out at
About 300c for example. thats not the case if i read the posted info correctly
The data stated that the temp range is independant on "manufacturing specifications" and not type
Also that the pt100 cannot be used without a daughter board thats because of the onboard resistor used doesn't match with the pt100.
Did i get it right ? -
What the limit of the device was i asumed the two were of diferant uses the tp100 being toped out at
About 300c for example. thats not the case if i read the posted info correctlyPt100 and Pt1000 can be used to about 800-1000*C however particular sensor might be limited due to other materials used in it.
Also that the pt100 cannot be used without a daughter board thats because of the onboard resistor used doesn't match with the pt100.
Basically Yes.
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Thanks ...again
i like the extra bits you guys put in. -
Also that the pt100 cannot be used without a daughter board thats because of the onboard resistor used doesn't match with the pt100.
Basically Yes.
It's a bit more complicated than just changing the resistor in the on-board voltage divider circuit to support PT100. Even if the resistor was changed for an appropriate one, I don't think it would be accurate or sensitive enough to provide good temperature feedback. That's why the daugtherboard uses the MAX31865 for precise feedback.
Ian
Bed-slinger - Mini5+ WiFi/1LC | RRP Fisher v1 - D2 WiFi | Polargraph - D2 WiFi | TronXY X5S - 6HC/Roto | CNC router - 6HC | Tractus3D T1250 - D2 Eth
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@droftarts In general Yes. I just simplified the answer. It could work with changing pullup but pt100 would draw significant current due to low resistance and would also heat up itself and this would lead to inaccuracy (and possibly could destroy platinum strip).
Best would be to use current source and amplifier, but MAX31865 for sure solves a lot of issues with reading pt100 (and also pt1000 with proper setup).
I could bet that it is more acurate to use PT100 with MAX31865 than pt1000 with simple pullup.
Measuring low resistances is a large topic itself, I just did not want to go into it too much.
SO pt1000 and some other thermistors have resistance that allow to match pullup resistor, that will not cause too much current flowing to heatup sensor significantly, and yet voltage drop on such sensor is still large enough that can be measured by ADC without fancy amplifiers etc.
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@BoA said in Termistor headache:
I could bet that it is more acurate to use PT100 with MAX31865 than pt1000 with simple pullup.
The accuracy of PT1000 sensors should be very good on the Duet 3 and Duet 2 Maestro and generally good on the Duet 2 Wifi and Ethernet. However, it may be poor on the Duet 0.6, Duet 0.85 and other SAM3X8E-based electronics. For these boards, you can calibrate the Duet's on-board analogue-to-digital converter to improve this
Then see https://duet3d.dozuki.com/Wiki/Connecting_thermistors_or_PT1000_temperature_sensors#Section_Temperature_calibration_and_ADC_tuning further down the page.
Yes, PT100 + daughterboard should generally be even more accurate than PT1000, and because it's a daughterboard, should be the same across all Duets.
Ian
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Thsnks much better inderstanding now and thanks for the links
