Resistance measurement

[ATElearner]

I got wrong resistance reading (does not match DMM) by using HP34970A due to caps in parallel. Would delay help? Which Labview driver shall I use to add delay?

Thanks

[LV_Pro]

Can you describe in a little more detail what you are measuring (what the circuit is) how you measured it with the DMM and how the HP instrument is connected. What Caps are in parallel, in what are they parallel with, etc. ? If you are using the HP instrument as a DMM it should measure the same as the manual DMM, if they are both being used the same. If the problem is a result of caps charging during the measurement then making repeated measurements until the measurement stabilizes (after the caps are charged) might be the way to get matching measurements.

[ATElearner]

We measure the output impedance of a power supply. I assume that the meter sees output caps, preload resisters, and high impedance of the load. The goal is the preload resister. When I use the regular DMM I can get the right reading of the resister but when I use Labview controlled HP I get something less. I am not familiar with the connection. I did use the same setup to measure an isolated resister and it worked. I have tried repeated measurements and it did not work. The reading stabilized at a lower reading.

[Jared_B]

ATElearner,

What happens when you take the reading from your HP34970A without LabVIEW being used?  Are the results the same or different?

[ATElearner]

If I just use “monitor” I got the correct reading but when I use “scan” without “channel delay” I got the same low reading as the one from Labview. After I added “channel delay” from the front panel and scanned again it worked. So I assume I should do the same thing to Labview.

 

But I do not have a driver that I can use to configure “channel delay”. Is there any example VI or driver with “channel delay” available?

 

Thanks.

[Dennis_Knutson]

Aren't you using one of these drivers?

[ATElearner]

Unfortunately the project is running on labview6 instead of 8. I did check the driver and did not see “channel delay” in the VI. I did not test the VI though.