Please. Help Me.. I'm newbie

Has anyone ever used sensor flow yf-s201 and pH sensor sku: sen0161? how to calibrate?

Those flow sensors are all much the same but usually have the pulses per litre written on them. If that one doesn't have the data somewhere, get one that does. They work really well, I think they are accurate to about 5% out of the box and, if you have something to compare it with, can be refined to 1% by changing the calcs in your programme.

Some guidance here Jaycar Water Flow Gauge | Freetronics

ok.. i'm try it.. thanks mister.