LabVIEW VISA Read Byte Count Limitations

[CWenger]

I have written a program that acquires and analyzes data from the Tektronix TDS3032B oscilloscope. The scope can transfer either 500 or 10,000 points. However, it seems the VISA Read function (I am using LabView 6.0.2) is unable of reading enough bytes to receive the entire data string. I am almost certain that this is not a timeout issue because I can set the timeout extremely high and still get the same behavior. What would be the best way to fix this problem?

[Lab Viewer]

I assume that you receive a timeout error when trying to read a big string (many points). Did you try one reading with a low byte count, less than the length of the expected string? ... or fast consecutive readings ?
If you are able to receive parts from the expected string, the problem looks to be buffer related. Thus, you can try to use "VISA Advanced > Interface Specific > Set I/O Buffer Size" to set enough room for a large string.

Hope this helps

[CWenger]

Actually, the error I recieve is that it has run out of system resources, when I use a byte count on the VISA Read function of 26,000 (it works fine with 25,000 but does not get the entire string). I highly doubt this though, since 26,000 bytes would be about 26 KB, and even though that is comparatively a lot of information, the computer I'm using has 512 MB RAM. Setting the I/O Buffer Size higher does not resolve the issue.

[JB]

Check if the last byte of the readings is always the same. If so, you probably didn't disable the use of a termination char. This will cause the reading to stop as soon as this byte is read.

For more information, see :
http://digital.ni.com/public.nsf/3efedde4322fef19862567740067f3cc/6e2c88c43c76a77386256975006db10a?OpenDocument

[CWenger]

I'm actually using a TCP/IP Instr VISA Resource Class an Ethernet port, in other words), and I may be mistaken, but I didn't think a termination character even applies here. Regardless, adding a property node to disable termination characters did not resolve the issue.