(i) To calibrate the given water meter
a) Water meter of size 25 mm with a needle and number gauge
b) Measuring tank of size .6x.6x.8 meter with over flow arrangement, gauge glass scale arrangement and a grain valve
c) Stop watch
Water meter is one of the most common types of quantity measuring meter used in pipe lines for measuring quantity of flow. In rotary type of water meter water flows across inclined passage where propeller is free to rotate. The propeller rotates due to the flow of water over the (gauges) vanes operates a series of gears. These gears are connected to the needle through a spindle. The needle rotates over a graduated dial, indicates the flow of water in liters. One revolution of the needle indicates a flow of 10 liters of water through the water meter; simultaneously the numbered gauge rotates by one division.
a-area of collecting tank in cm2
h-height difference of water in collecting tank
t-Mean time taken to collect 10 cm of water
(Qth) = (N*10*10-3)/tm
N-no. of turns of water meter needle
Tm-mean time taken
Error = (Qth – Qa) / Qth *100
Time for 10cm rise of water level (s )
Actual discharge Qa cm3/s
Theoretical discharge ,Qth, cm3/s
Coefficient of discharge Cd
Calibration of Water meter.
The quantity of water collected is compared with the number of theoretical quantity of water obtained from the meter reading. The difference gives a measure of the calibration of water meter.
- Open the inlet valve, keeping the outlet valve of pipe line connected with a water meter closed.
- Open the out let valves to allow to flow water through the water meter adjusting water valve to obtain 5 sets of reading.
- Note down the time for 10 cm rise of water in measuring tank simultaneously noting the number of revolutions of the needle and the initial and final readings of the gauge within given time
- Adjusting the outlet valve for the new flow rate and repeat the experiment
a) After completing the experiment close the inlet valve and outlet valve
b) Drain water from measuring tank after completing the experiment