GB1038287A - Calibration arrangement for flow meters - Google Patents

Abstract

1,038,287. Calibrating flow meters. ROCHAR ELECTRONIQUE. March 26, 1965 [April 1, 1964], No. 13044/65. Heading G4H. A flow meter is calibrated by passing through it a volume of liquid measured by a piston and cylinder producing a large number of pulses per circuit volume, the pulses being applied to a counter during an interval which is the time taken for the meter under test to register a given volume, the difference between the counter reading and a theoretical number giving the meter error. The cylinder 10 has its ends connected together via pipe 16 and the flow meter 18 under test. Piston 22 in the cylinder is displaced by nut 28 engaged with threaded rod 30. The rod is rotated by motor 34 through reduction gear 32 and a disc 36 on the rod generates photoelectrically a thousand pulses for each litre of liquid forced through the meter 18 by piston 22. The output pulses of the meter 18 are amplified at 46, divided by N (160) at 48 and applied to gate 50. The pulses from disc 36 are applied via gate 60 to counter 64. Gate 60 is opened for a measured interval by clock 62. A manometer device 44 measures the pressure difference alross the meter 18 and this is plotted at a on recorder 68. The output of divider 48 is plotted at b and is a square wave the duration of which is the time taken for meter 18 to make 160 revolutions, representing 10 litres. This signal opens gate 50 allowing the pulses from disc 36 to pass to counter 56. If meter 18 is accurate there should be 10,000 pulses during this period. The counter has four decades and should therefore return to zero. Any error is indicated on the counter, the value being complemented if necessary and the sign of the error indicated at 58. The speed of rotation of rod 30 may be varied to test the meter at different flow speeds. To test the tightness of piston 22 valve 40 is closed to introduce a restriction 42 in the meter loop. This increases the pressure differential on the piston and the leakage, if any. Tests are again made on the meter 18 and the results compared. If they are identical the leakage is zero. In a modification the piston is displaced in the cylinder by pressure generated by a pump. Displaced liquid passes through the meter under test and pulses are derived to measure the volume displaced by the piston as before.