How to set value of analog inputs to zero when there is no input

[jdub584]

Hi,

I'm reading in 128 thermocouples from a scxi but not all 128 analog inputs have a thermocouple attached.  For the analog channels that don't have a thermocouple attached, I want to read in a value of zero.  Is there a way to do this?

[AnalogKid2DigitalMan]

You could short the 2 input terminals together on each unused channel with a short piece of wire. This should result in a reading very close to zero.

[devchander]

I am not sure since I have not tried it out, but I think that shorting terminals might make you read the cjc value for that channel instead of 0 deg.

One way I did was to program a logic to detect all open TC channels in the read data ( they would be reading a saturated value at around max or min set for that cahnnel) and then,  I would use array operations to replace that channel's data with an array of 0's

Message Edited by devchander on 11-05-2006 11:02 PM

[50ohmTerminator]

Hi jdub584,

Some SCXI modules have Open Thermocouple Detection circuitry and I believe this is what you are looking for. There is an excellent Knowledge Base article describing it and how to use it. You can find the article by clicking here.

Have a good one.

Malay Duggar
NI

[devchander]

Malay, guess you posted the wrong link. It brings you back to this page itself

Here is the link which I guess, Malay intended to post

And what I have observed is this: In SCXI 1102/B/C modules, open thermocouple detection circuit enables you to scan across open TC channels in your scan list without measurement errors, but it does not bring the open thermocouple channel's read value to 0 deg C/F

[jdub584]

Hi,

The open thermocouple detection knowledge base did the trick.

Thank you all for the help!

[50ohmTerminator]

Thanks devchander. That was indeed the link I intended to post.

Glad it all worked out.

Cheers
Malay D
NI

[devchander]

jdub584, good to hear that it got solved