I am using a nice new LED stroboscope to measure water flow on a flow switch made by Proteus.
It has 6 paddles arranged every 60 degrees around the circle, symmetrically arranged, and water forces it to move in response to the flow. There are several flow models in this line.
You can measure the actual flow with a stroboscope.
So I find the lowest PPM setting at 387 pulses per minute, which if the same paddle is shown in the same position, that would be the same as the RPM'.
So you can get other numbers to stop the paddles,
like this: (all in Pulses per minute)
387, 450, 538,677,904,1361,2696.
I see two problems here. One is why don't they go up linearly, these numbers are anything but linear.
The second problem I see here is there are 7 numbers, not 6. Since the paddles are arrange in a hex pattern and are exactly 60 degrees apart, how does a strobe manage to stop the image on the last one, 2696 ? All the other numbers from 60 PPM to 10000 or so do not stop the paddles, hold them steady.
Only those 7. But why 7 and not 6? And why are they not a time sequence more in line with the paddles being 60 degrees apart? I think it safe to say the lowest frequency that gives a steady paddle image would be the actual RPM's and the other numbers stopping them would be 60 degrees shy of the paddle reaching top dead center and here are the numbers I calculated should be showing if things were linear: (rounded off)
At 387 RPM there should be about 0.025 seconds between paddle wheels (each 60 degree jump) so subtracting .025 from the original, inverting and multiplying by 60 for each one gives numbers I think they should be reading:
387, 461, 571, 750, 1090, 2000. Notice how the entire spread is smaller than the list I gave at the beginning. Why aren't I reading #'s more like those?