Digital Multimeters (DMMs) and Precision DC Sources

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NI-4065 measuring continuously

Hey guys,

 

I got my hands on a NI 4065 which I want to program with labview (the last time doint that is about 5 years past, so please forgive my at best mediocre skills...)

 

I had a look at the provided examples and the "cont Acq & Chart Multiple Samples" seems good for a first test. I would add saving the data to a tdms file which doesnt seem too complicated.

But there is one thing I struggle with: It seems the rate the measurements are taken is about once per second? I really need to speed things up because I want to monitor a resistance that will change much faster than this. Is there a way to speed things up? The change in resistance will be (possibly) quite big so I wouldnt need accurancy thats lower than 1 Ohm.

 

Thanks and regards
Bastian

 

 

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That example shows fetching a fixed number of samples per iteration (Samples to Fetch at a Time). If this number is small, it is very likely that the program is falling behind the true rate of acquisition of the DMM, and the DMM's FIFO is filling up (aka "the backlog").

 

A more efficient way to do things is to call niDMM Read Status.vi inside the loop. This will return the Backlog, which you will then pass to Number to Fetch input of niDMM Fetch Multipoint.vi.

 

But of course, make sure to reduce Resolution in Digits to speed things up in exchange for less precise measurements.

Marcos Kirsch
Chief Software Engineer
NI Driver Software
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Thanks, Ill look into that.
What do you mean by calling the Read Status.vi?! Is this Vi in the examples library?

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niDMM Read Status.vi is on the NI-DMM Fetch subpalette. I recommend you take a look at the "Maximizing DC Reading Rate.vi" example.
Tobias
Principal Software Engineer
Driver Software
National Instruments
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