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pulling accelerometer waveform and spectral data to the DSC database

Hello all,

 

I am working on implementing accelerometers in a rotating machinery engineering lab and would like to pull my raw time waveform data and my spectral waveform data from the accelerometer to the DSC module database.  For clarification, I will be pulling the RMS value of the acceleration to a single network shared variable at a high frequency(minutes), and will only want to pull raw time waveform and the spectral waveform hourly or daily depending on the duration of my testing.

My thought is to send the data to a network shared variable that is set as an array of doubles. I know I will probably need to send some additional data to help decipher the waveforms.  I am not sure if this is the best option, or if there are some best practices that exist for dealing with this type of data.  

 

Thanks,

 

Matt

 

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Your concept of "high frequency (minutes)" and mine clearly differ!  I think 1KHz is "moderate", and you are talking in milli-Hz ...

 

I'm not sure why you are talking about Network Shared Variables.  Are there multiple computers involved?  If this is a single PC running multiple (simultaneous) processes, all in LabVIEW, I'd use a Queue, a VIG, some other "safer" form of communication.  Your data rates are slow enough you could even punch a paper tape while the data are being collected and read the paper tape when you want to process it (what?  paper tape?  what is this guy talking about?).

 

Bob Schor

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Bob,

 

Thanks for the reply.  I apologize for lack of clarity on my part.  

 

The data is being pulled from several different machines through cRIO and cDAQ.  I will eventually have a few hundred accelerators and microphones pulling data simultaneously and dumping it to the database.

 

I am doing two things with the data.  One is the "slow" pull of the overall rms vibration as a single value (I'm also pulling temperatures, loads, flows, torque, etc to the DSC with this method.  I understand this part.  The part I am unsure about is the high speed time and spectral waveforms, which will be a few seconds worth of data, but at a data rate between 12 and 52 khz. The time between these high speed waveform acquisitions will be on the order of hours to days, so there will be a large time gap between each waveform.  

 

Hopefully that helps it make a bit more sense.

Thanks,

Matt

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So your question becomes "How do I transfer about 100,000 samples (order of magnitude) to the DSC every few hours?", right?  I'm assuming that you have enough memory in the cRIO to hold all the samples, so the transfer can take place as a single block when the sampling is finished (or, if the sampling is on-going, you can "sequester" this block and transfer it in a Consumer loop).

 

I've become a fan on Network Streams for transfer of data.  It is fast, robust, uses TCP/IP (so you don't have to worry about packet order), and fairly easy to setup and use.  There are Examples included (Help menu) that show you how to set it up.

 

Bob Schor

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If you are going to eventually be logging a bunch of data to a citadel database I would do a quick back of the envelope calculation to figure out how much data you are going to be storing and how fast you will be trying to write this to the database. Citadel is an easy to use historical database but the general suggestion is to keep the active database below 2GB in size which isn't a lot for certain application. Of course you can always archive the active database to back up all the data and keep the active database small but then you lose a lot of the advantages of having it be easy to access.

Matt J | National Instruments | CLA
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How is waveform data transferred to Citadel?  I can see how it could be done pt by pt but it seems that Citadel does have a native waveform data type, is this something only the deprecated vilogger had access to?

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I think you are looking for this information:

 

Waveform Data to Citadel

 

Also, this post is from awhile ago!  I'd create a new discussion thread if you are having issues.

 

-Bear

Regards,

Ben Johnson
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