How to get the r.p.m of a small pump from the water flow?

[veiledcavalier]

hi,

i have a small pump with: 220-240 v, 50 HZ, 30 w, 0.2 A,
and WATER FLOW: 20 L / min

i want to get its r.p.m ???

thanks

 

[Prototyp_V1.0]

Re: pump r.p.m

There may be two ways yuo can achieve this, but it depends all on the pump itself.

1)
If there is any rotating part (rotator) that is partial outside so you can see ant touch it, you can paint a black dot on it and place a optical sensor so that you can measure every rotation.

2)
The pump is already equiped with a rpm signal wire. But it's very unlikely. It's a pump indeed.

My guess is that the pump use a one phase AC motor wich means that the rpm is all depended of the ac frequency. In other words, the rpm is already fixed and measuring it would be a waste.
Would't it be more interesting to measure the flow itself?

 

[kender]

Re: pump r.p.m

1)
If there is any rotating part (rotator) that is partial outside so you can see ant touch it, you can paint a black dot on it and place a optical sensor so that you can measure every rotation.

Using a Hall-effect sensor would be a ramification of this method. If you have a shaft, which you can put a steel bar on, you can sense the passage of a bar as it rotates with a hall-effect sensor. If the pump assembly has a cooling fan driven from the same shaft as the pump, you can put steel screw into the blades (symmetrically, to maintain the balance of the fan) and sense the screws with Hall-effect sensor. You can, of course, sense blades with IR sensor too.

Tell us more about your pump. Post some drawings pictures or datasheets, so that we can understand the nature of the beast.

My guess is that the pump use a one phase AC motor wich means that the rpm is all depended of the ac frequency. In other words, the rpm is already fixed and measuring it would be a waste.

If the RPM is known, it’s possible to tell that the pump has burned or stalled.