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Problem With Resistance - Continuous Input Example on Labview example page

Hello!

 

I need to run this exact code for a continuous acquisition of resistance on sensors I am using at school. Once I select the dmm channel I get this error message:

 

Error -200077 occurred at Property Node DAQmx Channel (arg 6) in DAQmx Create Channel (AI-Resistance).vi:1->Resistance - Continuous Input.vi

 

Possible reason(s):

Requested value is not a supported value for this property. The property value may be invalid because it conflicts with another property.

Property: AI.Excit.Src
Requested Value: External
You Can Select: Internal

Channel Name: myDAQ1/dmm

Task Name: _unnamedTask<A>

 

But when I change the excitation to internal I get this error message:

 

 

Error -200077 occurred at Property Node DAQmx Timing (arg 1) in DAQmx Timing (Sample Clock).vi:1->Resistance - Continuous Input.vi

 

Possible reason(s):

Requested value is not a supported value for this property. The property value may be invalid because it conflicts with another property.

Property: SampTimingType
Requested Value: Sample Clock
You Can Select: On Demand

Task Name: _unnamedTask<C>

 

I dont understand why it is so difficult to just take the data and write it to a file. I want a graph to display too but writing it to a readable file is most important. Thank you!!!!!!

 

 

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Message 1 of 12
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What exact example? You need to be a little specific.

As you can see from the specs, the dmm is software timed so if you are specifying a sample clock, that would be the source of the error. The solution is to place the dmm read inside a loop. The rate will be slow and have jitter.
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Message 2 of 12
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Hi Dennis!

 

It pops up as an example VI under the Labview Example Finder once I searched measuring resistance. It's titled Resistance - Continuous Input.

 

The error pops up at the start VI (the excitation error), so this should disappear once I put the read VI in a loop? I was testing some loop configurations out but I think I forgot to try that one.

 

If I try using the Analog outputs instead of dmm do I have to do the same thing? I was getting similar errors when I tried this method too. Thanks so much!

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Message 3 of 12
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You can filter examples based on device.

You have to remove all functions related to setting a sample clock. You have to remove everything related to taking more than one sample. You have to remove evening related to an external excitation.

An analog output is not at all the same thing as the dmm. The dmm is an input.
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Message 4 of 12
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I'm sorry but I don't see what is so mysterious. Clearly all DAQ devices do not have the same features or capabilities. Consequently all examples do not work equally well with all devices. So in your case you picked an example that has two settings (at least) that are incompatible with your hardware.

Mike...

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Message 5 of 12
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Sorry, I meant analog inputs.

 

Okay so I got rid of the timing portion, and put the read/write sub VIs in a for loop instead. The only problem Im having is getting rid of the external excitation source. When I try to change it to none, when I run it it automatically changes it back to external. Since it's part of the create channel subVI I do not understand the way around this.

 

Thanks!

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Message 6 of 12
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Can you post your latest VI?

 

Things don't just automatically change back and unless there is something programmatically telling it to change back.

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Message 7 of 12
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You're not doing something as silly as opening the subVI and changing the value on its front panel, are you?
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Message 8 of 12
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Here are my attached VI's. Im thinking it will be easier to go with VI 2. When you double click the create channel in VI 1 that is how the excitation source is adjustable but it wont stay when I change it.

 

Also am I doing my for loops correctly? Im just trying to obtain continous sample point readings when I hold the dmm plugs on a resistive strain sensor. From here I want the continuous points to save in one text file!

 

Thanks so much for the help.

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Message 9 of 12
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Double clicking a subVI and changing the front panel is just silly as I said. The setting has to be on the block diagram of the main VI. Right click on the input to the subVI and select Create Constant.

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Message 10 of 12
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