0 volt reading occasionally from Agilent 34410A

[BurningH34t]

I've been using the 34410A drivers in labview (specifically "read single measurement") to obtain a voltage. Essentially, I put that inside of a loop so it will measure a voltage over and over again which gets logged (upwards to 600+ times). The issue now is that occasionally, a zero volt reading will return in the log file. I thought it was a timing issue so I added a delay (100ms to 500ms) in between each read but I am still experiencing this issue.

Have anyone encountered this before or know how to fix it?

Thanks!

[RavensFan]

Are you checking for errors from your Read functions?  You might be getting a communication error, and as a result the default value for the data which would be zero.

[BurningH34t]

Note: This is all from the Agilent 34401 driver for labview... I have a power supply connected directly to the DMM, so it's measuring at all times.

There is an error check at the end of the read (single point). vi that "check for questionable data warnings and instrument errors" but it does not trigger when a 0 volt reading returns... What I did find is that under the fetch measurement (fast read).vi is where the measurements come from. There is a case structure in here where true = "If there is data in memory, then read", else "If there is no data in memory, then just pass through".

I'm guessing at a random occurance, the device thinks there's no data in memory and so returns a 0 even though there should be a value?

In any case, is it possible to fix this?

Thanks again.

[MoReese]

Are you sure your instrument is not reading 0V?  What are you measuring?  Have you tried stopping the program when this happens to see what your variable and memory contents are at that time?  Once this occurs, stop the program and do a secondary read (automatically or manually) and see if you get the same result.  This system may be simply returning what it sees.

[Packers4]

Anyone have an answer for this. Im having the same problem.

[Packers4]

Did you ever find anything out on this?  Im having the same problem.

[MCOTO]

Hi,

Is this happening so often? I mean, how much times on a log of N samples do you get this behavior?

[Packers4]

It is random. It may be 1 time out of 100 samples or 2 times out of 1000 samples.  Instead of using the Read(Single point VI) I wrote a VI that uses the MEASURE command instead of using the FETCH and READ commands that the Read(Single Point VI) uses and it solved the problem.  I havent got a 0 reading yet.

[MCOTO]

Great!!!

[Chien_Nguyen]

it seems to me that by adding an Autozero.vi (Once)  funtion before the Initiate Measurement.vi will solve the problem. Until now, running the program with 10 samples/sec for 25 mins without any 0 volt reading.