Taking Fast Measurements with Labview

[Matt C.]

Hi everyone,

I'm attempting to make fast voltage vs. time measurements on a voltmeter. The measurements have to have a frequency of 10 - 20 ms to be meaningful to me. I'm simply using a Keithley 2000 Multimeter instrument driver to take multiple measurements, so it does no additional calculations other than recording data. However, I noticed that there is an inherent delay in every measurement of about 3 ms, and this builds up to a significant delay when I get to hundreds of measurements. I looked at the Keithley datasheet, and they claim to be able to take about 2000 measurements every second, so I don't believe that the problem is the instrument, but rather the built in delay of LabView.

Is there anything I can do about this delay, or will I simply have to correct for it when we get the data?

Thanks,

Matt

Message Edited by Matt C. on 01-21-2009 12:42 PM

Message Edited by Matt C. on 01-21-2009 12:43 PM

[Dennis_Knutson]

There is no 'built in delay in LabVIEW'. How are you calculating the delay? The multiple measurements should start as soon as it is triggered and the interval between measurements is up to the instrument. When you use the Data Read Multiple, you get an array of values all at once. I have not dug into the driver or looked at the manual but maybe you are missing some setting that sets the measurement interval.

[AnalogKid2DigitalMan]

Readings/second is based on how many digits of resolution the meter is set to, suggest you review the manual.

-Ak2DM

[Albert.Geven]

Hi

You are forgetting the communication delay between the coputer and the instrument.

If you program the keithley to do a measurement this fast it can only measure not communicate.

So you have to be sure that the data fits in the local datbuffer in the keithley !