Agilent 34980A (with 34921A module) returns an incorrect 1st measurement with READ?

[JamesEdward]

Hello all!

I'm trying to get to the bottom of an intermittent issue that we've had for a while.  Sometimes, the first measurement returned from a scan does not match the rest of the measurements.  In fact, the measurement looks like it belongs to the previous scan!

I have not found what is triggering it.  It is not solely a hardware issue, as it only appears while testing certaint variants of our product.

I've already created this thread on the Agilent forums, where a lot of my details are recorded:

http://www.home.agilent.com/owc_discussions/thread.jspa?threadID=37537&tstart=0

I'm using:

LabVIEW 2010

Test Stand 2010 SP1

Visa commands to talk to the Agilent

I'm using the Agilent for both switching and measurement functions.

I'm sure there are moredetails you need - let me know and I will add pieces of code, settings etc.

Thank you!

James

[MajorTom]

Hi James,

Can you include pieces of your code and the setting that you are using?

[Dennis_Knutson]

I've recently used that instrument and did not notice any such problem. Are you using the LabVIEW driver? Do you see the problem with one of the examples in the llb?

[JamesEdward]

MajorTom:

A lot of my settings aren't located within the code.  I will do my best to give you all the needed information (without dumping my entire project here).

Config DMM:

The case typically used is the "DC Voltage" Case.

Set Scan List:

Takes an additional reading for each channel (intended to be a "band-aid" for this issue).

Read DMM:

Throws out first reading for each channel (intended to be a "band-aid" for this issue).

In my code, the process is usually:

Config -> Set Scan List -> Read DMM

However, sometimes I will read multiple times before resetting the scan list, or set the scan list multiple times before configuring.

Please let me know if I need to provide any more information.

Thank you for all your help,

James

[MajorTom]

Hi James,

I just want to clarify, are you experiencing problems with LabVIEW or with TestStand?

[JamesEdward]

I have not found what the actual culprit of my problems is.  I am using LabVIEW 2010 with Test Stand 2010 SP1.  I may be mistaken, but everything that talks to the Agilent is within a LabVIEW module.

It is possible that the problem isn't in my code at all, and is a bug with the Agilent.  On one hand, there is nothing (that I've found) that would cause this behavior in my code.  On the other hand, this issue only appears when testing certain variants of our product--the code changes slightly depending on the product.  But the only difference between the two variants' test code (that relates to the Agilent) is related to switching certain channels on the Agilent.

Thank you!

James

[MajorTom]

James,

The code looks good to me as well, do you experience any issues running the shipping examples for that driver?