Hi Ed,

I knew it is not an easy task to get such system going especially when in my application the transmitter will be above and bellow water at times. I will try some other avenues first and if no success I might bother you with some more questions.

I will be away from my office for a few more days so I do not have access to my notes.
For our test we just calculated the speed of the jet and the volume of the water passing through in a time period. With the water density as a constant we were able to calculate the thrust.
In your case I’m quite sure you will need at least your differential pressure, the surface of the sensor (maybe) and the water viscosity. I will look into getting you a formula combining all the factors from which you can extract the speed as the only unknown.

What will be an acceptable size for the paddle wheel? The one I used was a little over 1” diameter and it is used on Sea-Doo PWC for speed indicator. It gives 4 pulses per revolution and it is a completely sealed unit wit three wires interface (power in and signal out). If you are interested I can send you one as soon as I get access to it. Just PM me your address and you will have a possible back up solution.

For the differential pressure method how hard will be for you to take a couple of readings at half and full speed to see if your numbers will make some sense. From that it will only be a matter of coding.

Regards,

Nick