Subject: Timing issues in LabVIEW 6.0

[andrewW]

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

[ian_fung]

hi, i may not have a solution for your case but I am using Agilent's Multimeter and I do not have such problem of what you mentioned.

Just some thoughts; would there be any chances that the multimeter is limiting the read-op? Streaming the read-data to binary file format might help?

No offence, just some thoughts.

[andrewW]

Ian,

I wish I had a newer multimeter...

> Just some thoughts; would there be any chances that the multimeter is
> limiting the read-op? Streaming the read-data to binary file format
> might help?
>

I suspect there is a way to coax the read operation to execute faster,
but the instruments in question have no commercially supported
drivers I know of so I have to employ trial and error...

> No offence, just some thoughts.

None taken. The thoughts are appreciated.

[Dennis_Knutson]

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

[andrewW]

Many thanks for the tip, Dennis!

Dennis Knutson skrev i
meldingsnyheter:506500000005000000EDA50000-1031838699000@exchange.ni.com...
> 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.
>
> 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 i
n LabVIEW but you should be able to use the same GPIB
> commands.

Message Edited by Molly K on 02-18-2005 11:38 PM