Subject: Timing issues in LabVIEW 6.0

Question

Hi all!
I am running LabVIEW 6.0 on Win 2k Professional and am baffled
by the following:
Using the GPIB Read .vi, I read from a couple of virtually
identical Solartron/Schlumberger 7150 Digital Multimeters at
a set time intervall and subsequently write the data to file.
The test routine performs only elementary arithmetic besides
GPIB reading and writing to file.
Using the Get Time/Date In Seconds .vi to time the read-store
loop reveals that the GPIB Read operation is excessively slow.
As the GPIB Read .vi's timeout defaults to 10000ms (488.2
global timeout), I tried out a number of different timeout
values and found that timing only begins to approach the
value I set without GPIB read errors when timeout is set at
>=1000ms and th
e read-store intervall is at least 440ms(!)
I cannot understand why the GPIB read operation should
require as much as 440ms when the CPU is otherwise minimally
loaded...
Isn't there a way to GPIB read at a rate faster than once
every 440ms?
Thanks in advance.
Best regards,
Andrew

Answer 1

I did a quick search of the instrument driver network and found a CVI driver for your instrument and a LabVIEW driver for a model 7151. You can convert the CVI driver to LabVIEW and the 7151 might be close to what you need. The drivers can be found here: Solartron 7150 LabWindows/CVI Certified Plug and Play Instrument Driver.
Also, there could be a lot of reasons that your readings are slow. See if Solartron has some example code that you can look at. It probably won't be in LabVIEW but you should be able to use the same GPIB commands.Message Edited by Molly K on 02-18-2005 11:38 PM