Detect breakdown voltage in an AC waveform

Question

I need to monitor an AC Voltage waveform and record the RMS value when the breakdown happens. I roughly know how to acquire data from videos I have watched, however, it is difficult for me to produce a solution that reads the Breakdown Voltage Value. Ideally, I would also take a screenshot along with the breakdown voltage value,

In case you are not familiar with this topic, When a breakdown happens the voltage will drop immediately to zero. So what I need is to measure the voltage just before it falls to zero, and if possible take a screenshot. This is an image of a normal waveform (black) with a breakdown one (red).

Answer 1

Naive solution*:

1. Take the data and get the Y values (this would depend on the datatype you have, which would depend on how you acquire the data).
2. Find the breakdown point by iterating over the values and maintaining a couple of flags (I would probably say track "got higher than X" and once that's true, track "got lower than Y").
3. From that, I would just say take the last N points (Get Array Subset) and get the array max. Or just track the maximum value as you run.

Assuming you have the graph in a control, you can just right click and select Create>>Invoke Node>>Export Image.

I would suggest trying playing with that with a VI with static data which you can repeatedly run to check how your code behaves.

*I don't know the problem domain and an not overly familiar with the various analysis VIs that ship with LV, so there are quite possibly more efficient ways of doing this.

Answer 2

It is returned in the stored order (order in the file), but it is not guaranteed to be that they are in the inserted order. They are not sorted by the _id field. Sometimes it can be look like it is sorted by the insertion order but it can change in another request. It is not reliable.