A mechanical Master PD Flow Meter is fitted with a Rate of Flow Indicator, Unit Drum attachment and a Veeder Root Counter. The unit drum facilitates to read-off fractions of litre (or deca-litre) and the final reading can be accurately read to 0.05 litre (or 0.05 deca-litre). The unit drum, positioned below the counter, consists of a
graduated circular drum with vernier scale marking. The mobile unit consists of a mobile trolley on which the Master PD Flow Meter is mounted, alongwith inlet and outlet hose connections to connect the Master PD Flow Meter in series with the field flow meter.
The procedure for checking is simple. The Master Flow Meter is connected in series with the field flow meter, either by connecting it in the field flow meter's pipe line or with the help of rubber hoses. After priming the system, counters of the test flow meter and the Master Flow Meter are zeroised and the adjusting ring of the unit drum is turned so that the zero marking coincides with any graduation on the unit drum. A fixed quantity of liquid, say 1000 ltres is then passed at a constant flow rate and then respective readings on test flow meter and Master Flow Meter counters are noted down. Master Flow Meter's fractional reading is noted from the unit drum. After applying pre-established correction factors to the Master Flow Meter's reading, the corrected reading is then compared with the test flow meter's reading to calculate the inaccuracies of the test flow meter.