cro like waveform

[rk_t]

Hello all,

In my application I am capturing a waveform across a shunt which is in series with a motor.

I am attaching the waveforms observed on CRO and using Labjack U3 hardware.

I am not able to capture the same nature like I observe on CRO.

Voltage setting on CRO is 0.1V and time setting is 2ms.

Can anyone please help.

Thanks

[rk_t]

here are more images

[rk_t]

more images

[rk_t]

more imagfes

[altenbach]

Instead of attaching 10MB worth of pictures, you could just attach the code and tell us what should be different. Don't have us stare at a dozen pictures trying to figure out what you want and don't want.

Who wrote the LabVIEW code?

• Building an autoindexing array at a while loop boundary will eventually consume all your memory and slow down the loop. How long do you typically run this before you press the stop button?
• Why are you configuring the AI every 2 ms over and over again. Wouldn'd once before the loop be sufficient? (Especially since the controls are outside the loop, so changes to them during run will have no effect).
• If you use acronyms, tell us hat they mean. "cro" is not a common term.
• What is the voltage range of the signal? What is the frequency? How is the labjack configured and connected?
• Where did you get the drivers? Does your code resemble some example program?

[rk_t]

Hi Altenbach,

First of all sorry for that many images.

Secondly, the labview code is an example code from labjack website.

here is the link: https://labjack.com/support/software/examples/ud

Following are the answers to your questions:

• Building an autoindexing array at a while loop boundary will eventually consume all your memory and slow down the loop. How long do you typically run this before you press the stop button? ANS: This was just was my demo purpose.
• If you use acronyms, tell us hat they mean. "cro" is not a common term. ANS: CRO is a Cathode Ray Oscilloscope.
• What is the voltage range of the signal? What is the frequency? How is the labjack configured and connected?   ANS: The singal varies between 0 to 5 v(max). Labjack U3 HV is connected via USB for this.
• Where did you get the drivers? Does your code resemble some example program? Link posted above.

Also attaching the vi.

I am using labview 2009 on windows 7 platform

Thanks

[altenbach]

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@rk_t wrote:

Secondly, the labview code is an example code from labjack website.

here is the link: https://labjack.com/support/software/examples/ud

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What's the name of the example. I could only find a similar example without the while loop.

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@rk_t wrote:

• What is the voltage range of the signal? What is the frequency? How is the labjack configured and connected?   ANS: The singal varies between 0 to 5 v(max). Labjack U3 HV is connected via USB for this.

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I was more interested how the signal is connected to the Labjack. (the USB side is not interesting ;))

You still did not reveal the frequency of the signal. You seem to take one point every 2ms (software timed).

[rk_t]

Hi,

I used the attached example code.

Frequency may vary from 1kHz to 10kHz depending on the motor.

I did not configure the labjack. I just connected it via USB and used this program.

[altenbach]

That's what I thought. This code acquires only a single sample point. You (mis)placed a FOR loop around it that runs every 2ms (or slower if the code takes longer than that). So you get 500 points per second in the best case and there is no way that you can measure frequencies of 1-10kHz. You cannot measure a high-frequency signal by sampling an occasional single point.

As a first step, look up Nyquist.

[rk_t]

Thank you for your response. I did go throught the link.

What should I do next in order to get the results?