SCXI-1001 thermocouple measurement issue

[k_norr]

Hello,

I am having an issue with thermocouple measurements using an SCXI-1001 chassis with SCXI-1102 modules. Basically, the measurement will look like open thermocouples on all channels and stop all of my tests (they have an upper limit of 100C imposed by the software). Below is some more information about what I have going:

System description:

 - PXI-1045 chassis with PXI-8186 embedded controller, (1) PXI-6052E DAQ, (4) PXI-6704 Analog Output modules, and (4) PXI-2467 Relay Driver modules

 - Running Windows 2000 with software written in VB6

 - MAX version is 3.1.1.3003

 - DAQmx version is 7.3.0f0

 - SCXI-1001 chassis with (4) SCXI-1102/SCXI-1303 for thermocouple measurements and (4) SCXI-1104/SCXI-1300 for voltage measurements

 - Both the SCXI and PXI chassis are plugged into a 1500VA UPS

Some observations:

 - All three fuses on the SCXI chassis checked out okay

 - If I try measuring a thermocouple in MAX just after the problem occurs, it gives me error 200073

 - Currently, two SCXI-1102 modules and two SCXI-1104 modules are not being used and do not have the SCXI-1303 or SCXI-1300 terminal blocks

 - When the problem occurs, if I turn the SCXI chassis off, wait 30 seconds, and turn it back on, it will work, but all thermocouple measurements will be ~23C, no matter how hot or cold the actual thermocouple is. It will keep running like this until the problem occurs again and hits the upper software limit. In order to make it read correctly, I have to turn the SCXI chassis off and on like any other time, but also have to restart the test software (not the entire OS, though). Then it works again for a little while.

Please let me know if any more information is needed and thanks in advance for any help.

Ken

[Hesloppy]

Hi Ken,

That is interesting.  Has this system worked in the past?

What is the range your modules are set to?

Best Regards,

[k_norr]

Hi Bryan,

This system has worked great for about 5 years and then started acting up. Half of the SCXI-1102 module channels are set to 0V - 10V, the other half are set to -5V - 5V. All of the SCXI-1104 modules are set to -0.01V - 0.01V (we're measuring temperatures between 20C and 100C.

Also, the UPS on this system has been acting up lately. Could this have anything to do with it?

Thanks!

Ken

[Hesloppy]

Hi Ken,

I don't think the UPS would be causing something like this.  It could be that there is a bent pin or lose connection on the modules.  Can you try removing them and putting them back in?

Also do you see the same behavior if you just run a simple example? 

Best Regards,

[k_norr]

Hi Bryan,

What do you mean by a "simple example"? I'm running one thermocouple channel in MAX (continuous sample) to see if anything happens there.

Ken

[Hesloppy]

Hi Ken,

Do you mean that after it hits the limit it reads incorrectly in MAX too?  I was suggesting to just run a program that only reads in the temperature.  MAX is also a good place to test it.

Have you tried resetting the devices?

Best Regards,

[k_norr]

Hi Bryan,

If I shut down my program without turning anything off and then open MAX and try to access a channel, it will give me the 200073 error. Once power to the SCXI chassis is cycled, it works fine in MAX. However, it will only read ~23C in my program. The only way to get the system to run correctly (at least until the glitch occurs again) is to cycle power to both the SCXI and PXI chassis.

I've been running one channel in MAX for several days now and there is no error.

Thanks,

Ken

[The_Red_Barron]

Howdy Ken,

You said that the system runs correctly after cycling power to everything until the glitch occurs again.  How long does it take for the glitch to occur and is it something that is predictable?

Although it's unlikely, it might be possible that if your UPS is glitching it could cause a strange power flucuation in the SCXI that interrupts communication and cause the problem.  Can you try running the system with a different, stable power source to see if it functions without glitching there?

Regards,

[k_norr]

Hello Barron,

I changed the UPS to a new one and it still failed. It never happened in a predictable manner, but always within a couple days of when the system was restarted. I did, however, have to replace the battery packs that were being tested and did find a thermocouple wire that had a very small place where the insulation was not there. This just happened to be in a place where it could, under certain circumstances, make contact with a cell in the pack and send a high voltage to the SCXI thermocouple measurement module. I fixed this and it's been running for about a week with no issues. Hopefully this solved the problem. Thanks to you and Bryan for your help!

Ken

[helen82]

I am getting the same problem as yours. I tried my best to solve it, but up to now it's been still. Hope someone help us to deal it soon.