University task

[Kmist]

The raw signal from human walking is given in a separate LabView VI called “Pressure
signal.vi”.  This VI simulates the raw signal received by the pressure sensing mat and you will need this signal as your input.

How do I do the rest of these steps?
2. You will need to design a data acquisition system to analyse this signal.
3. You need to extract the signal after filtering the noise, amplifying to Volt level, displaying signal
in time and frequency domains.
4. You need to display your results on the front panel including raw waveform, filtered waveform in time domain, filtered waveform in frequency domain, walking frequency in Hertz, control options to change filter parameters.

[Bob_Schor]

You need to go to class, stay awake, write little VIs that illustrate the principles discussed in class, write little demo routines, write bigger demo routines, make up problems and write them in LabVIEW, program, program, program.

If something isn't clear, you need to ask your instructor to explain it.  It's also a good idea to get to know your fellow students so that you can "teach each other".  True, in the Time of Covid, this is a little more difficult, but Teams and Zoom allow you to share screens ...

If you have some code that "sort-of works" but something doesn't quite work, post your code here and ask a specific question.  If we "do your homework for you", you aren't going to learn, and should probably just drop the class.

Bob Schor

[Kmist]

It's true, I do need to do more work on it, but I've gone through the lectures and other materials and I still don't understand how to do the task. 

In most cases I've found people are working with external devices and using the DAQ function to process the data, however for this case the lecturer's given me this 'Pressure signal' array, with no explanation on what the numbers mean or how to connect it to the rest of the circuit.

I've reached out to my lecturer but he isn't the best at replying.

My intention wasn't to find the exact solution to this problem, only an insight into how to extract information from the 'Pressure signal'.

If you don't want to help me with the rest of the questions that's understandable but please help me understand what the numbers on the right are representing.

Thanks 

[Kyle97330]

What you are showing there is an array of waveforms.

For each waveform:

t0 = time zero, the start time of the waveform (in this case, no start time is specified, it's zero)

dt = delta time, the time between each point on the waveform (in seconds, so in this case the data is 0.001 seconds or 1 ms apart)

Y = An array of all of the data collected.

If you were going to put these on a graph, for each Y value, you could calculate the X value as being :

t0 + [dt * (Index of Y in the array)]

[Bob_Schor · Accepted solution]

To expand a bit on Kyle's reply:

• Array of Waveforms.  How do you know it is an Array of anything?  By the Array Index control on the left and the box that surrounds the inner "whatever-that-is" that make up the contents of the Array.
• Array of Waveforms.  So what are the elements of the Array?  When you see different Elements grouped together in a Control or Indicator, particularly if they have individual "labels" like "t0", "dt", or "Y", you are dealing with what LabVIEW calls a Cluster, and C/C++ call a "struct" (I think -- Pascal calls it a Record, and I know Pascal much better than C).  Notice that Y has multiple elements showing, along with an Index (the double-headed arrow shows where it is) -- another Array.
• Because LabVIEW is designed as an "Engineering Workbench" (the "EW" of "LabVIEW"), "sampled data", consisting of data ("Y") acquired at fixed sampling intervals ("dt") starting at some initial time ("t0") are sufficiently common that they designed a separate Data Type for Data Acquisition (abbreviated DAQ).
• So your picture represents a data sample, acquired at 1 kHz (since dt = 0.001 seconds, and f = 1/dt).  This represents the first sample (since t0 is 0), and the Y values represent measurements (of whatever is being measured -- notice that the values are floats, probably Dbls, and probably 1000 of them, but I'm just guessing here).  If you wired this thing into a Waveform Chart, you'd plot out the data when you ran the code (and could see what was being measured).

Bob Schor

[Kmist]

Thank you!