Setting Input Resistance on the PXI-4071

[Jeffrey_Zola]

The specifications for the PXI-4071 DMM indicate that the input resistance can be chosen as either 10 MOhm or 10 GOhm for the 100 mV, 1 V, and 10 V ranges. I see where this can be input on the instrument soft panel, but I have been unable to locate how to configure the input resistance when using the DMM in a VI. Suggestions?

Thanks!

Jeff

[crossrulz · Accepted solution]

You need to use a property node.

[Jeffrey_Zola]

Ah.  Looked at the Property Node, but didn't go deep enough. Nor could I find it in the help files or any of the other online documents.

Thanks!

Jeff

[Jeffrey_Zola]

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@Jeffrey_Zola wrote:

Ah.  Looked at the Property Node, but didn't go deep enough. Nor could I find it in the help files or any of the other online documents.

Thanks!

Jeff

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One other somewhat important detail I found necessary: You must use the "Change All To Write" option on the menu that comes up by right-clicking on the Property Node. Otherwise, the DVM remains with 10MOhm impedance.

Just thought I'd add this for those who search for this thread later on!

Jeff

[Now_With_Underscores]

Hey Jeff,

That is correct.  Otherwise, you're simply reading the input resistance, which by default is 10MΩ.  Let us know if you have any other questions!

[Sparks!]

So close, yet still so far from an answer. Being a NI Knight, you know exactly what to do. Trust that I have "known exactly what to do" in diverse fields. No, LabView is not one of them, in spite of the time I have invested in learning.

Here is the problem: I need to use input resistance >10GOhm to measure the DCV of a precision reference. I can do that in the SFP by clicking a box. But, I want to have a log and can do that in Python using NIDMM. Fine, however the voltage is lower when on 10MOhms than on the higher resistance. I have spent a few hours on this without finding a simple solution for a trivial task. 

The Property Node--however useful--does not appear by itself and I am not able to find anything that matches your excellent diagram.

[kirsch]

Hi @Sparks!

You are reviving a 12-year old thread. I didn't quite understand your message. Are you trying to set the input resistance for an NI-branded DMM using the `nidmm` Python module?

Or are you using the NI-DMM from LabVIEW and don't know how to find the property node?

Please clarify and let us know what particular DMM model you are using.

[Sparks!]

Well, I managed to locate the "Property Node" near the bottom of the NIDMM instrument librarian LabVIEW and following the "map" provided earlier, got the ">10GOhms" enabled in LabVIEW. Not in python . . . Yet. 

NI4071.input_resistance = 10000000 in a python script does in fact set the property, however the DMM does not seem to be informed, and so remains at 10MOhms. Not what I need.

There also seems to be a problem with enums not being recognized, but that will probably be resolved in a reboot. Sigh . . .

[kirsch]

It seems you solved your original problem (how to configure the Input Resistance property in LabVIEW).
But you have a second problem: configuring input_resistance property in Python does not seem to be working.
And a third problem "enums not being recognized" (in LabVIEW? in Python?).

You should start a new thread for each specific problem and provide detail so that we can help you. Specific models and driver versions and example code are very helpful. Thanks.

[Sparks!]

Hello Marcos!

Yes, to both questions: I'm working with LV18 and vintage NI gear, so a 12-year old answer will help. Testing a voltage reference 10 VDC, I noticed a difference in readings when SFP was set to >10G vs. the 10M. I normally run Python scripts to log the output for use later. 

Finding the "Property Node" took a while, but now I know how to get to it. I could create a vi and use win32client to work in python.

I would much prefer to not go that way and just set the property in python. Setting input_resistance for NI PXI-4071 in python seems to work in that I can use print to see the value I put in.

The NI 4071 does not implement the property. Using SFP DMM set to >10G, an overnight run showed min max difference only in the sixth decimal--that's good--so I would like to see the full reading in a python log.

Any idea why 4071 is not recognizing the property?

Thanks,

Donal