Electrical Engineering. Delay or phase difference of a voltage signal adquired by RedPitaya.

[lucialucilu]

Hi!

I'm working with Labview and RedPitaya in order to measure Voltage and Current to calculate  the instantaneous power that an elevator consume when it is working and afterwards see how much is active P and reactive Q.

I have to measure Voltage between line and neutral and multiply it and the current, the problem is that the neutral is not accessible, so I have to measure line to line voltage and turn it into line to phase voltage. 

In order to accomplish that I have to make two changes. 

1) I have to /sqrt3. That I have already done without problem

2)I have to set a phase difference of 30º, or a delay of the equivalent time (1.6666667 ms) to the voltage signal.

I have tried to accomplish this by using a wait block in a while structure, but it doesn't work properly when the voltage needs a loop, because the subVI is not running at the same speed when reading current and voltage after a delay as I see with the highlight option. And all the clock, wait or delay blocks that I have seen are supposed to work in a loop, not wired to a signal that an instrument is reading and acquiring.

Is there any way to set this phase difference or an equivalent delay without a loop that affect only to the voltage signal??

Thanks in advance.

[Daikataro · Accepted solution]

Have you considered just asking for all the samples, then discarding those you do not require? For example let's say you are sampling at 10kHz, so each sample equals a 100us period, 16 samples equal 1.6ms and so on. So you multiply sample 0 of line 1 (0 indexed array) by sample 15 or 16 of line 2 (whichever one works best for ya, or an average of the 2) and use that as your result. That way you don't need any delays whatsoever, and don't have to worry about sync, since all data is coming at the same time