SR830 VERY unreliable data transfer

Question

Please help!
I am using the Stanford Research SR830 Lockin Amplifier and I need to transfer the data from the instrument buffer to my computer. Usually this would just be a simple GPIB write/read sequence. I am using the SPTS? command to query the number of points in the buffer and the TRCL? command to write the data into the I/O buffer. The program sometimes runs successfully but in most of the cases it fails. It seems there always remains some garbage in the buffer or that the transfer is not ready when I want to read the data.
I looked-up the LabView help and fell on the concept of Service Requests. I subsequently modified the program to include SRQ. This should prevent that I read the data too early. So a typical command sequence would be *CLS;*SRE16;TRCL?1,0,{number of points}
So how does this work? *CLS; should clear the whole status register; *SRE16 enables status bit number 4 (2^4=16) which is the service request bit. The vi SRQ wait should continuously query when the SRQ status bit changes. All this should make the data query much more reliable. In practice what happens is that the VI waits in wain for SRQ until it times-out. I put the time-out value up to 60 seconds, this should definitely be enough to transfer 1000 data points. I don't understand what is wrong. I also tried the NI packet GPIB spy to monitor the traffic on the GPIB bus and everything seems to be normal. I attached the Labview library. Any ideas?
Attachments:
SR830_VISA_binary_transfer.llb ‏91 KB

Answer 1

Hi David,
I noticed you said you used GPIB spy.  I was wondering what version of the 488.2 and VISA drivers you had? 
Also, I was wondering if you had tried using the LabVIEW instrument driver for the SR830?  If you have a 488.2 instrument, you should be able to use this driver.  There are a few exaple vi's including a Data Storage Example that recovers data from the instrument's buffer.  It may be worth a look if you haven't already tried it.
Hope this helps!
Adam W
National Instruments