agilent 34970A serial communication

[JFMoynihan]

I'm trying to communicate with the agilent 34970A using a serial connection.  I set up the connection in MAX and verified communication by sending a few commands and queries.  No problem there.  When I switch to LabVIEW 8.5, I use the EZ Temperature.vi, but I get an error on the Read portion of the process.  If I attach a terminator (\n) to the end of the command string generated in the EZ Temperature.vi, I get a write error.  If I connect to the GPIB bus, there is no problem.  I've read many posts about this but most are a few years old.  Can anyone give me a tip on this one?  Thanks.

[mfitzsimons]

Sounds like a driver issue.  To be clear the same everything (serial cable, equipment, and PC) works in previous version of LabVIEW.  Correct?

[mfitzsimons]

Also, not all serial cabels are created equal.  Try a different serial cable if you have one available.

[JFMoynihan]

Matt,

Thanks for the reply.  I'm adding this feature to an existing LabVIEW 8.5 application, so it was not part of any previous version of the software.  I am on my second serial cable, and the communication is good with MAX.  That's the sticking point for me.  The EZ Temperature.vi is simply a visa write and a visa read.  It's my understanding that the VIWrite and VIRead in the MAX test panel are accomplished using the same vi's.  In the past, I've been able to introduce a time delay between the write and the read, but in this case, the time is critical and I don't have much to play with. 

[mfitzsimons]

Serial can get inconsistent when you don’t give enough time between reads and writes.  The first thing I would do is give it a long delay between reads and writes to see if it behaves correctly.  Then reduce the time until it starts acting up.  Add a bit of extra from the point where you start to see problems.  This is the empirical method of figuring out the best timing.   Let me know if a longer delay fixes the issue.  Also, if you are moving lots of data you may have some buffering issues.