Resize Data Record for Post Processing

[mallorim]

Introduction

Sometimes data needs to be acquired at a certain sampling rate with records of a required length. However, when processing this data, it might be advantageous to have the ability to resize the record lengths.

The VI below takes the acquired data and breaks it into records of a smaller size. For instance, with every iteration of the while loop, 16,384 samples are read. You can use processing to break these samples into 16 sections of 1,024 points. Something to note is that you will only be able to evenly divide into the acquired samples.

This is done with a nested for loop. The outer for loop iterates once for each channel of acquired data. The interior for loop, uses a user defined constant to break the acquired data into that many chunks, iterating once for each chunk.

Now in order to perform post processing on these smaller chunks of data, they will need to be bundled back up into waveforms, each with their own unique t0 intial time. The waveform datatype consists of three pieces, the intial time t0, the time between samples dt, and an array of amplitudes 'y'. B y taking the oriinal t0, and looking to see which iteration our for loop is on, we can add time to the t0 to determine the new value for that data chunk. We then bundle it all together and perform the desired processing on the signal. This is what the VI below does.

Steps to Complete

1. Update the DAQ assistant to reflect your device names and the desired channels and sampling rates.

2. Add the processing necessary for your application. In the image above, an fft functino can be seen. The required controls and displays will need to be added.

Additional Notes

For more information on the Producer/Consumer Architecture, see this tutorial.

In order to see how to created longer chunks of data, rather than smaller, see this community example.

Since this processing can be time consuming, you would want to take advantage of the Producer/Consumer architecture in order to seperate your processing from the data acquisition. This will keep the data acquisition from experiencing buffer overflow and overwrite errors.