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grounded TC error

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Hi,

I have a problem reading from a TC ( K or J ) hooked to my PCI-MIO-16XE-50.
I have the TC connected to channel 15 in single ended mode. The dip switches
are set with the on board TC set to single ended channel 0.

If I read the Temperature with the TC laying on my benchtop then it reads
correct. As soon as I connect it to my equipment which is grounded stainless
steel I get huge errors. The signal seems to pickup lots of negative noise
( -200C )

I have tried to put a 4.7K ohm resistor and a small cap on the signal but no
luck.
Any ideas?

Thanks a bunch






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It's sounds like you have a problem with ground. I saw a very similar problem
(although not using NI equipment). I was using a digital thermometer plugged
into a wall outlet and a T thermocouple. I was trying to measure the
temperature of the chassis of a piece of equipment that was grounded through a
wall outlet. Whenever I touched the thermocouple to the chassis I got very wild
readings. Switching the digital thermometer over to batteries fixed my problem.

I'm not familiar with the PCI-MIO-16XE-50 board and I obviously don't know
anything about the equipment your trying to measure the temperature of, but it
may help to take data differentially instead of single ended. If you can, you
might also try shutting off the equipment and removing ground from the
chassis
(if it's as simple as unplugging the AC input) and retry measuring temperature.
That might tell you if it's a grounding problem or not.

Doug Richardson wrote:

> Hi,
>
> I have a problem reading from a TC ( K or J ) hooked to my PCI-MIO-16XE-50.
> I have the TC connected to channel 15 in single ended mode. The dip switches
> are set with the on board TC set to single ended channel 0.
>
> If I read the Temperature with the TC laying on my benchtop then it reads
> correct. As soon as I connect it to my equipment which is grounded stainless
> steel I get huge errors. The signal seems to pickup lots of negative noise
> ( -200C )
>
> I have tried to put a 4.7K ohm resistor and a small cap on the signal but no
> luck.
> Any ideas?
>
> Thanks a bunch
>
> If replying to my email remove nospam from the name
0 Kudos
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(1,112 Views)