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Intermittent OPC timeout on E4407B

Question asked by seanj on Feb 25, 2011
Latest reply on Sep 12, 2014 by generald

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Hi All,

I am trying to do a simple channel power measurement wth 25 averages at 10.525GHz.

After the channel power measurement I run an *OPC? command to be sure it has worked. I am seeing that intermittently the OPC will not complete and times out after 10 seconds. The E4407B is being used in a customer system and we had thae customer on site. The sequence ran fine for 20 runs and then failed for with an OPC timeout error. This is most certainly not a good thing to happen in front of a customer.

I had been using an E4405B but recently changed to an E4407B. I had hoped that maybe the OPC error was related to the E4405B, where is also appeared intermittently but this was not the case.

Does anyone know why I am getting these intermittent timeout errors?

Thanks,
Sean

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tabbott Mar 1, 2011 4:18 PM
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Hi Sean -

What is your timeout in your program set to? Perhaps you need to increase it.

Perform the measurement manually and get a rough count on how long it takes to do the 25 averages. Things like RBW/VBW and number of sweep points can affect the sweeptime, which can affect the length of time it takes to do the measurement. You need to make sure your timeout is set long enough to do the measurement. *OPC is just going to report when the operation is complete after the 25 averages. If you don’t want to do this test manually, increase your timeout in your program to something large and then retest. It sounds like your timeout is too short and perhaps right on the edge.

I hope this helps -
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tsilchia Mar 2, 2011 11:51 AM
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Hello,

My experience in programming and automation with the SAs is a bit limited as I usually reside in the Network Analysis group. Regardless, any chance on those intermittent failures the SA went into the dreaded "Internal Alignment" routine thus increasing the time to complete the averages? I know on the PSA I worked with you could disable the internal alignment too. Alternatively you could forgo the *OPC? command and mask the correct SRQ and Status Bytes for *OPC (i.e. operation complete condition - not as a query) and then use an interrupt on SRQ to auto sense the operation complete bit being set in the status register. This *OPC method with an SRQ removes any chance of a timeout error and is not dependent on the instrument timeout setting in the development environment.

Sincerely,
tsilchia.
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seanj Mar 23, 2011 7:39 AM
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Hey Guys,

Sorry for the delayed response. I didn't get a mail to say that I had got a response and thought there had been no response.

The timeout is currently set to 20s, I've reconfigured the averages from 25 to 5. This should only take about 1.5s so it leads me to believe that 20s should be sufficient.

The dreaded internal alignment! I recently had to do a system allignment as it prompted me on the display. Is "dreaded internal alignment" something different?

I'm going to loop the program and try and capture the moment of failure by spying the GPIB port. If I can reproduce the fail, I will post it here.

Thanks for the suggestions,
Sean
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tsilchia Mar 23, 2011 7:44 AM
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Hello,

One in the same.

What language are you programming in?

Can you provide a snippet as text of 5 .. 10 lines of code which we could run in a loop to emulate your configuration and sequence.

What is the firmware version on the SA?

Sincerely,
tsilchia.
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seanj Mar 23, 2011 9:07 AM
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Hi tschilia,

I am using TestStand and labVIEW for the communications and the Agilent driver set. I am currently looping the first two tests which are
1. Centre Frequency
2. Channel Power

I've been doing this for over an hour with no failures to date.

I've attached a file showing all the commands that are used.

I've been seeing an intermittent fail for the channel power, usually when I go home and run the test overnight I see a timeout error when I come back in the morning. This is not good. The program must be capable of running for months without stopping rather than hours.

All suggestions welcome. Would be interested to know about the "dreaded internal allignment", perhaps the temperature is dropping/ rising during the night.
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- Capture.txt195.4 KB
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pjonesco Mar 25, 2011 10:09 AM
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Interesting, I too am having a similar issue. I am using Matlab though. The timeout error occurs after more than hour of normal operation. I tried doing some manual GPIB commands, while having the 'dreaded alingment routine' running and the commands work fine. I also cannot detect that the alingment is in progress. *STB? always returns 4, even when the alignment is running. Also, I cannot find anywhere the definition for the STB register.
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pjonesco Mar 25, 2011 10:27 AM
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I am acutaly using he N9030A, not the E4407B.
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seanj Mar 28, 2011 2:17 AM
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pjonesco,

I wish I could say I still find it interesting, it is very annoying at the stage.

I managed to capture the failure as it happened in the attached file.

The spectrum analyzer stuck at channel power measurement e4407b and would not respond to local/system button or even the off button.

Any help appreciated.

The labVIEW error appears as follows:

Error, VISA Write in Wait for Operation Complete.vi->E4402B OPC.vi->E4402B OPC.vi.ProxyCaller VISA: (Hex 0xBFFF0015) Timeout expired before operation completed. [Error Code: -1073807339, User-defined error code.]
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- Timeout Error edit small.txt232.0 KB
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- a1penguin @ seanj on Mar 13, 2014 5:52 AM
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  Hi Sean,
  I am wondering if you ever resolved this issue. I am having a very similar thing on a 9030. It will work fine for weeks and then all of a sudden, I get the freeze-up. This has been going on for years and nothing I have tried has helped. I have played with the gpib timing in MAX, I have taken out the *opc and replaced it with hard coded wait times set to longer than a sweep. I have played with the visa timeout parameter. Frequently, the lockup occurs during the setting of the reference level and attenuation, but not always.
  
  Edited by: A1Penguin on Mar 13, 2014 6:47 AM
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- generald @ seanj on Sep 12, 2014 3:34 PM
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  I'm seeing the same problem on a E4407B, firmware is A.14.06. Very annoying as you can never tell when it will happen or any indication as to what the error is. No error coding.
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Intermittent OPC timeout on E4407B

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