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GPIB processing seems to take a very long time
Frieda
Member
03-30-2005 05:26 AM
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I am running an electromagnet from a DAQ card (Ni-488) and reading the field from a multimeter (keithley) via a GPIB cable into a PCI 6014 card. The data aquisition via the GPIB seems to take a really long tme though, in the order of a second per datapoint. Is this normal for this kind of setup, or are there any parameters that I can adjust to make this time shorter?
Thanks!
Thanks!
Dennis_Knutson
Knight of NI
03-30-2005 10:05 AM
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I don't understand the relationship with the GPIB instrument and the 6104 DAQ board but the GPIB communication alone could take some time depending on how you're programming it and the instrument capabilities. What software are you using? Is it LabVIEW with a driver? What's the model number of the DMM? If you're using LabVIEW with a driver, what function in the driver are you using? A high level function such as a Getting Started VI takes a relatively long time because it sends quite a few commands to initialize the instrument before retrieving a measurement. You should also check the instrument manual and see if you've set it up for the fastest possible measurement. Some things like autoscaling and extended resolution slow it down. If you could post the program that you've written, it would help to diagnose the problem further.
03-30-2005 04:45 PM
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I think you are right in that the driver is the problem. it is a keithley 195A with a very simple labview driver. The driver is one single sequence, which means that it is initializing and telling it the settings every single time for every single datapoint. Do you think that I could use the driver from a more advanced keithley multimeter, whcich decouples the initialization from the data processing?
Dennis_Knutson
Knight of NI
03-30-2005 05:13 PM - edited 03-30-2005 05:13 PM
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I don't know if you could use an actual driver. The commands could be completely different. You could certainly download one and compare syntax. At the very least, you could use it as a model for modifying the existing one. Writing drivers is not all that difficult. There's a great set of guidelines available here. If you go this route, be sure to get the LabVIEW Development Tools". You could also use a couple instances of the Instrument I/O Assistant (assuming LabVIEW 7 or higher). You could have one that does all of the initialization at the beginning of your program and another that does nothing but take the current measurement. Since all of the instrument's command are in the driver you have, it should be pretty simple.
Message Edited by Dennis Knutson on 03-30-2005 04:15 PM
