chart history data

[Greg Cole]

Hi all,

Just trying to understand the data here. What type of data am I
getting when I use a property node from a chart (with 3 channels of
daq info displayed) to extract the history data? It appears to be a
2-d array, part of which I am sure is the wave data type for each
channel, but I can't figure it out exactly.

The prompting for this is: After I have run a daq routine to acquire
my data, I want to take the data from the chart (via property:history)
and send it to a subVI where I will process and return it for writing
to a file by another subVI.

The problem arises in getting the process subVI with the correct
inputs to where I can extract channels and process them, rebundle and
send back.

Thanks for any info.

Greg Cole
gcc9@cdc.gov

[Shan]

The data structure you get out of the History property depends on what you put into the WF Chart. It sounds like you're inputting an array of waveforms. If this is the case, use Index Array to pick out a specific waveform you want to process. You can then use any of the Waveform Measurements or Waveform Operations vi's found in the Waveform palette. If you need to do something that's not available there, you might have to break out the "y data" using Get Waveform Components.

If your still stuck, post an example of what you're doing and we'll take a look.

Tim

[Greg Cole]

I have done some more investigating and believe I have part of the answer.

The Chart History data is a 2 dimensional array of waveform data type.
The data in the chart is broken up into "History Length" pieces, creating
the 2nd dimension.

For example:
Chart history len = 1000
I record 10000 scans of 3 channels
Chart history data will be a 10 x 3 array of WDT data.

I'm hoping I can get the length set high enough that I can always keep
the result to a 1 x 3 array. Still experimenting on that.

Greg

Shan wrote in message news:<50650000000500000033D70000-1042324653000@exchange.ni.com>...
> The data structure you get out of the History property depends on what
> you put into the WF Chart. It sounds like you're inputting an arr
ay
> of waveforms. If this is the case, use Index Array to pick out a
> specific waveform you want to process. You can then use any of the
> Waveform Measurements or Waveform Operations vi's found in the
> Waveform palette. If you need to do something that's not available
> there, you might have to break out the "y data" using Get Waveform
> Components.
>
> If your still stuck, post an example of what you're doing and we'll
> take a look.
>
> Tim