Thermocouple reading in SCXI 1000

[arsjzy]

I have an SCXI-1000 chassis. I'm trying to read 4 T type thermocouples. All things are fine when I establish the first channel. When I estbliash the second and third channel, all the TCs show around a fixed temprature, 19 or 20 C even when I put them into ice water. But when I do the calibration, all the chennals still show accurate tempratures. After I cancel other channels, the first channel turns to show the accurate temprature again.   

[KathrynTheGreat]

Hi Arsjzy,

Is the one working channel always the same channel, or do all of the channels behave as expected, as long as you're only measuring one? 

It would also be helpful if you included a snippet of the code you're using to bring in the data.

[arsjzy]

Hi, Kathryn

The temprature is shown as expected when there is only one channel. After I pluge more thermocouples and set up other channels, all tempratures are the same, even when I put TCs into ice water or boiling water(just very little fluctration around a fixed number like 19, 20C). But when I go into the calibration part, they all show the temprature as expected. Then they all show the same fixed temprature again( not the channel 1 temprature) when I run it.

So it's too strange why every channel works in the calibration part but not in the run part. 

I have not done the code part. The problem is in the DAQ input setting up process.

Thank you for your help.

[KathrynTheGreat]

Hi Arsjzy,

How interesting.. just to be clear, each channel works individually in when the program is run, or is it only the first channel that works on its own?

In other words, assuming you're using AI0, AI1 and AI2, and knowing that you don't get the expected values when measuring all 3 at the same time, or even 2 of the 3, have you gone through and run the code measuring only AI0, then again measuring only AI1, then only AI2?

What do you mean when you say "the calibration part"? Are you talking about running a Test Panel in NI MAX?

Also, have you gotten the chance to include a snippet of your code? It's hard to narrow down the underlying cause without seeing the code that's having the issue.

[arsjzy]

Hi, Kathryn

I mean when I only go through channel AI0, the temprature is right. Then I set up another channel AI1, work on them both,the two temparatures are in a fixed number(still a very small flactration around it), neither the right tempature of AI0 or AI1. It is same when I use more channels. So it shows right temprature when I use only one channel.

The calibratin part means in DAQ Assistante properties-configuration-thermocouple set up-calibration. In this part, all tempratures are right when I use more than one channel. But all tempratures are still not right when I run the code.

Here is my code attached.

[Great-Britton]

Hey,

What happens if you read the values coming directly out of the DAQ Assistant?  If you see the same behavior coming out of the DAQ Assistant, could you post a screenshot of how you have that thing configured?

If you're getting correct values out of the configuration screen, but not your code, then the problems got to be in there somewhere, either in how you have the DAQ assistant, or the statistics VIs set up.