Pt100 sensor settings Problem

aidar

@Inno-3D said in Pt100 sensor settings Problem:

M308 S0 P"spi.cs1" Y"rtd-max31865"

Also try spi.cs0 instead of cs1, assuming your PT100 sensor is connected to first port of daughterboard.

droftarts

@aidar said in Pt100 sensor settings Problem:

Also try spi.cs0 instead of cs1, assuming your PT100 sensor is connected to first port of daughterboard.

I initially thought that too, but actually the pin names (listed here https://duet3d.dozuki.com/Wiki/RepRapFirmware_3_overview#Section_Pin_names_for_Duet_2_WiFi_Ethernet) are
spi.cs1
spi.cs2
spi.cs3
spi.cs4

Ian

Dougal1957

Also a pic of the daughter board wiring would maybe help as well

Inno 3D

@droftarts Yes you are right now it shows 2000 degrees

@Dougal1957 here is a picture:

Dougal1957

@Inno-3D said in Pt100 sensor settings Problem:

@droftarts Yes you are right now it shows 2000 degrees

@Dougal1957 here is a picture:

Remove the jumper and you need 2 that short the pairs together ie across pins 1&2 and 3&4

it needs to be the same as the other port on that board

droftarts

@Inno-3D @Dougal1957 is correct, you need jumpers on all four pins if you're using a 2-wire PT100. See https://duet3d.dozuki.com/Wiki/Connecting_PT100_temperature_sensors#Section_To_connect_a_2_wire_PT100_sensor

Recent production PT100 daughter boards (v1.1 or later see the image above) have 2 sets of 2 jumper pins per channel. Install jumpers on those pins.

Ian

Inno 3D

@Dougal1957 @droftarts Ah ok I've got it wrong.

Many thanks for your help!!
It's working now!

Dougal1957

@Inno-3D said in Pt100 sensor settings Problem:

@Dougal1957 @droftarts Ah ok I've got it wrong.

Many thanks for your help!!
It's working now!

Glad you got it working.
You had effectively shorted the sensor which is why you got -273.1 an open gives you the 2000 reading (Normally)

Doug

droftarts

@Dougal1957 said in Pt100 sensor settings Problem:

You had effectively shorted the sensor which is why you got -273.1 an open gives you the 2000 reading (Normally)

It's the other way around: -273 means open circuit (ie nothing connected, infinite resistance), +2000 means short circuit (ie no resistance, because the jumper was on), because the resistance of a typical 100k thermistor decreases as it gets hotter. The PT100 and PT1000 are different, as the resistance increases as the temperature increases, but (I think) the chip on the daughter board inverts this and sends a reading to the Duet that works in the same direction as regular thermistors.

However, his initial -273 was because the tool was referring to a heater and temperature monitor that wasn't defined.

Ian

Dougal1957

@droftarts said in Pt100 sensor settings Problem:

@Dougal1957 said in Pt100 sensor settings Problem:

You had effectively shorted the sensor which is why you got -273.1 an open gives you the 2000 reading (Normally)

It's the other way around: -273 means open circuit (ie nothing connected, infinite resistance), +2000 means short circuit (ie no resistance, because the jumper was on), because the resistance of a typical 100k thermistor decreases as it gets hotter. The PT100 and PT1000 are different, as the resistance increases as the temperature increases, but (I think) the chip on the daughter board inverts this and sends a reading to the Duet that works in the same direction as regular thermistors.

However, his initial -273 was because the tool was referring to a heater and temperature monitor that wasn't defined.

Ian

Thanks for that Ian I din't know about the inversion in FW I did however know how the PT100 responds to changes in Temperature.

Doug