Hi I'm getting strange readings on my NI9211 (used with USB carrier) when trying to take a measurement. I have the NI9211 and a Eurotherm 3216 controller connected to the same unsheilded grounded thermocouple (diagram attached). I realised this isn't best practice, but I have no alternative, and have used the set up successfully in other systems. I'm using this set up for 3 thermocouples & 3 controllers sharing 3 channels on the same NI9211. With one TC connected to both the readings are fine, when I connect a second is when the readings are changed. I always get the correct reading on the Eurotherm. It was suggested to me I should use resistors to link the negative legs of the thermocouples to the common on the NI9211. I've tried this with limited success. It seems to only work at certain temperatures. Any ideas how I can correct it?

Multifunction DAQ

Thermocouple measurement problems using NI9211

Author

Hi Peter,

Sorry I've not logged in for a long time!

I wouldn't have thought you needed the resistors in channels that are not being used. I don't have a solution for this. All I can suggest is to systematically work through what may have changed.

Message 11 of 12

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These controllers support MODBUS

Why not use it to read the temperature values?

Greetings from Germany
Henrik

LV since v3.1

“ground” is a convenient fantasy

'˙˙˙˙uıɐƃɐ lɐıp puɐ °06 ǝuoɥd ɹnoʎ uɹnʇ ǝsɐǝld 'ʎɹɐuıƃɐɯı sı pǝlɐıp ǝʌɐɥ noʎ ɹǝqɯnu ǝɥʇ'