SCXI Possible Grounding Issue?

[Smroz]

I have a TBX-1303, hooked to an SCXI 1102 module, im reading voltage signals, I connect a couple signal conditioners these output 4-20mA connect a 250ohm resistor across them and they output 1-5VDC. they operate normally as to be expected based on the signal conditioner input and read with a multimeter. once i connect them to the 1303 card they load up and output roughly 12VDC and the resistor gets hot. i have tried different cards, terminal blocks, and signal conditioners they all do the same exact thing. this 1303 card has numerous different signals being input in the same way a 4-20mA output with a 250 ohm resistor across and i have no issues with them. i have tried powering the signal conditioners from different sources, inputting calibration signals rather than sensor signals and have no luck. i have tried grounding the inputs through a 100k resistor called the manufacturer of the signal conditioners and they recommended grounding the inputs. i am at the end of my rope any thoughts??

[Smroz]

Looks like i possibly stumbled on the answer. i hooked it up using a TBX 96 terminal block and it works just fine... could have been somthing to do with the common mode voltage driving my signal conditioners nuts. but i will verify with the manufacturer to find out what they used during their evaluation of the system.

[Travis-E]

Hello Smroz,

The TBX-1303 includes circuitry for signal conditioning specifically for thermocouple measurements. A typical thermocouple measurement is on the order of millivolts and there is an amplifier which scales that up to volts. If you are applying a signal that is on the order of volts then you are probably amplifying past what the rails of the card is, this would explain why the resistor is heating up. you don't see this in the TBX-96 since there is not amplifying circuitry.

Regards,

-Travis E