[hotrod]

One possibility for a low tech electronic blocked jet detector would be to use a pressure drop across another orfice up stream of the jet.

[ jet]---------------[psensor 1]----------[orfice]----------[psensor2]--------[control solenoid]-------------[pump]


If you were to put a configuration like this in place. I would expect to see:

1. solenoid off, both psensor 1, and psensor 2 would have an equal low pressure approximately equal to the intake air pressure.

2. solenoid open, jet flowing normally, psensor 2 would have a pressure reading near line pressure but slightly higher than psensor 1 due to flow induced pressure drop across the orfice.

3. solenoid open, jet clogged, psensor 2 and psensor 1 would have equal pressures at line pressure.


Not sure if you could find a good balance in size for the orfice so it did not unnecessarily restrict flow but still induces enough pressure drop for a comparator to detect and light a warning light.

The bad news is you would have to calibrate it for each jet size, as changing the jet size or even the supply pressure would alter the pressure drop across the orfice.


The electrical equivalent to the hydraulic circuit would be:


[load resistor]----[ v1]------[voltage drop resistor]----[v2]-----[relay]---[battery]


You would be detecting the hydraulic equivalent to the change in voltage drop across the dropping resistor if the load resistor fails open, or very high resistance.

You might be able to subsitute a final filter for the pressure drop orfice and use its pressure drop. You would then be able to detect both blocking of the final filter, and blocking of the jet, or no pressure at the jet when the solenoid triggers indicating no water flow (reservoir dry or pump failure) when the system should be spraying.


Larry