temperature jump when stop and go measurement

[gill]

I am doing a simple temperature measurement using LABVIEW 6 SCSXI box and K thermocouples. When stop the measurement after runing a long time, changing the file name where the data are recorded and continuing the measurmeent a jump of 6 degree is observed . . The temperature has no reason  to jump like that. I do not know the reason for such a behavior is this because of the software?

Thanks

gill

[Elijah_K]

gill,

I have a few troubleshooting questions for you that might help narrow down your difficulties:

Are you stopping the acquisition when you change the file's title?

Is the temperature accurate before the jump?

Is it always 6 degrees higher no matter the initial reading?

Does it stay at 6 degrees or does it come back down, and if so, after how much time?

If I think of more questions, I'll post them.

[gill]

Hello Elijah K,

the answers to your questions are:

1. Yes I stop the acquisition during changing the name of the file

2. I do not know if the measurement is accurate enough. Since I am interested in temperature differences I do not really care about absolute values. All the values (3 channels) are jumping with same quantity.

3. The jump is not always 6 degree this was only an example, depend also on the running time before I stop the acquisition and then run again

4. the temperature does not come back.

I was thinking that the reference temperature is measured only at the beginning. Then can be explained because in time the room temperature can change and during the stop and go the value is updated.

Thanks a lot

Best regards

gill    

[Elijah_K]

What happens if you don't change the filename, but just stop and start the task? 

What are the exact module numbers of the hardware you're using? Give me all the information you can and I'll try to reproduce the error on my end.

[gill]

Hello Elijah K,

The hardware components I am using are as follow

- data acquisition board PCI 6024E
- a chassis SCXI 1000 with module SCXI 1120 and connector block SCXI 1328.

The main point is that has to work for one or two hours and then stop and go.

Thanks a lot

Best regards

Virgil

[Elijah_K]

Hey Virgil,

This is a tough and unusual problem to isolate and troubleshoot.  I can't imagine why changing the filename would cause the readings to jump - that certainly isn't expected behavior and shouldn't be happening.

Do the readings jump when you stop the task and restart it without changing the filename?

Is the temperature reading accurate the first time?

Please try setting up temperature acquisition tasks in Measurement and Automation Explorer and monitor the measurement in that view to see if it also jumps.  If this works, then we'll know for sure that it's a problem with the LabVIEW application.

Let me know the answers to these questions when you get a chance and we'll take it from there.