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DMM 2535 Handshaking one scan multiple sample not working; V ok, R nok

Hey,

I'm using the DMM Switch handshaking example. It works as is, but:

1. keeping V measurement; changing continuous scan to FALSE; changing sample amount from 5 to 1; adding MUX leaving running state to continue to FETCH DMM; FETCH DMM with accumulated backlog.
STILL WORKS, BUT V values are wrong! 5.6V i.s.o. 0V !!

2. Corrected to work with:

- back to continuous scan (because single scan doesn't work (hangs in the mist somewhere) when more than 1 sample/trigger asked)

- multiple samples (e.g. 5) per trigger

NOW MEASURING CORRECT 0V

3. I want to measure R

DOESN'T WORK !! ALWAYS NaN i.s.o. e.g. 450 Ohm.

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Message 1 of 14
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Hi,

Can you share your code here so I can better understand where is this problem coming from? 

Thanks. 

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Message 2 of 14
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Hey,

in attachement You'll find the vi

regards,

Koen.

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Message 3 of 14
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Hi,

 

As I understand so far, you used a pre-written NI example and made some changes which produced unwanted results.

 

A good idea is to go back to the initial code and try to understand what impact has each change made on your results. In this way, you will identify what produces the unexpected outcome. 

 

Give me an update if this is working. 

 

Regards.

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Message 4 of 14
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Hello,

that was also my first reaction.

The outcome is as I stated that switching from V measurement to R measurment, the R measurement didn't give proper results.

V measurements were ok with all 0V (more or less. R measurements all gave NaN i.s.o. 460 Ohm (more or less).

There's a big difference between V measurement and R measurement, R measurement uses a predefined accurate current, may be because of that that the handshaking is wrong.

regards,

Koen.

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Message 5 of 14
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Hello,

 

I found some information regarding this issue. DMM/Switch handshaking works in LabVIEW 32-bit, but not in 64-bit. 

 

I have some more questions:

1. What LabVIEW are you using (version)? Is is 32 or 64 bit?

2. On what hardware are you running the code? What is your setup?

3. Why do you need to measure V and R? On what application are you working on?

4. What do you mean by a big difference between V and R measurement?

 

Regards.

 

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Message 6 of 14
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Good day,

I'm using 32bit version labview v16.

We are using a PXI1078 Chassis with DMM4065 & MUX2535. (more inserted: SMU4038 & MUX2575 & PSU4112)

We are testing PCBs on shorts, opens, voltages and resistors + functionality of relais.

To measure V, I assume the DMM doesn't need to inject a current.

To measure R, I assume the DMM injects a predefined accurate small current and applies R=V / I.

regards,

Koen.

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Message 7 of 14
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Hello,

In order to see where the problem is produced, I need to understand the system in more depth. 

 

1. The first step that we need to do is to check that the hardware is working properly. Try to see if the PCB is properly setup. 

2. With the PXI, try to see if the DMM measurements are working in NI MAX. You can do this by following the link below:

http://www.ni.com/tutorial/4638/en/

3. Try the NI MAX test using different PCBs.

 

If you still have the same results in NI MAX, it means that there is a problem with the hardware. If not, we can start focussing more on the software part.

 

Regards.

 

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Message 8 of 14
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Good morning,

we did checked it with MAX. The measurements were all right.

regards,

Koen.

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Message 9 of 14
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Hello,

 

As I understand so far, the DMM V and R measurements work fine in NI MAX and on the original example but when you make some changes on example VI you start receiving unexpected results. 

 

I have some questions:

 

Why do you need to make this changes in the VI?

Can you use NI MAX for making your measurements?

Have you made any progress in understanding why the unexpected results occur?

 

Let me know if the problem was solved.

Regards

 

 

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Message 10 of 14
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