What do I need to read 120 channels(input) of voltage (dual rail power supply range from -20v dc to +20v dc)?

[Henry_M]

I am working on a project that requires record data into excel sheet format. I need to read 120 channels of voltage. The voltage range is from -20v dc to +20v dc. After reading it, I need to format it into excel sheet. Does LabVIEW Base is good enough to make it done? Does LABVIEW have products that can read this voltage range? What else do I need to read all 120 channels? I am appreciated for any input.

Thank you.

[rolfk]

Lots of hardware and money!😀

LabVIEW itself is not the problem. What you want to do on the software side is something that a properly written LabVIEW program likely can do left handed while juggling an inverted pendulum in the right hand. 😀

But you forgot to mention another important factor. What’s the speed you want to read these channels with?

[santo_13 · Accepted solution]

DAQExpress and FlexLoggers are good out-of-box softwares for logging. You can still achieve the same in LabVIEW with good amount of coding depending on the UI/UX needed.

Have you decided on the hardware? Common DAQs support +/-10V ranges and not +/-20V range. Why the +/-20V range?

120 channels is quite a lot, probably better to go with PXIe system so you have better bus bandwidth to capture so much data.

[Henry_M]

The +/-20V range is what I need to measure. I don't know if I need something that take more than +/- 20v to avoid max out. I already tried my voltage divider. It worked, but I have a problem with -20v. 

[Henry_M]

I don't know the speed that I want to read from each channel because I got 80mv peak to peak (ripple) when I manually tested with probes. It is a switching power supply. So maybe 1 second is enough to read when it switches each channel?

[rolfk]

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@Henry_M wrote:

I don't know the speed that I want to read from each channel because I got 80mv peak to peak (ripple) when I manually tested with probes. It is a switching power supply. So maybe 1 second is enough to read when it switches each channel?

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You mean 1 sample per second per channel? What do you try to measure here? If it is about testing the power supplies then that would seem extremely slow. If it is just about monitoring the voltages it could be fine.

[santo_13]

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@Henry_M wrote:

I don't know the speed that I want to read from each channel because I got 80mv peak to peak (ripple) when I manually tested with probes. It is a switching power supply. So maybe 1 second is enough to read when it switches each channel?

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Have you finalized your hardware? If yes, what models? Are you confident that you've done due diligence for the application?

You've been providing bits and pieces of information; if you need better feedback, you must describe your application and requirements better.

[Henry_M]

I am choosing cDAQ-9189  with modules NI 9205. I just need 4 of the modules. But the range is +/-10V is the problem. 

I am still looking for modules that can take more +/- 20V. If I can't find one, another way is to amplify signal which I don't know how to do in LabView. 

I just accepted your early post as a solution and gave Kudos.

Yes, I am new to LabView community and everything. 

Thank you.

[Henry_M]

I never used analog input module of LabView before. I don't know how robust and precise it is. Yes I am testing the power supplies. 

Thank you

[santo_13]

Are all the 120 signals referenced off the same GND?

Note that 9205 is a multiplexed DAQ; this means there could be a ghosting issue based on the difference in voltage between adjacent channels.

https://www.ni.com/docs/en-US/bundle/daqhelp/page/multisimulsamp.html

https://knowledge.ni.com/KnowledgeArticleDetails?id=kA03q000000YHy6CAG&l=en-US

https://knowledge.ni.com/KnowledgeArticleDetails?id=kA00Z000000P84RSAS&l=en-US

Though you may be able to reduce the ghosting effect in some applications you may not be able to eliminate it and that could be a weakest chain forcing you to switch to different DAQ.

Now, if you're using external voltage divider to bring the signal into 10V range, you will definitely end up in the ghosting issue if you don't use a well designed OPAMP based divider. Now, given the external voltage divider, you accuracy of the signal now depends on how ideal your external circuit is (in some applications it is important, in some, not at all).