electromagnetic flow meter

[deepakdange]

i have developed 1.5" electromag. it works fine when straight run is there or on the mouth of pump driven by 3 phase electric motor.
but when the same pump is driven by hydraulic motor i get enhanced readings. viz.

pump rpm 1440 which is fix for both motors and let flow is 13.2 m3/hr on electric motor then it comes 24 m3/hr on hydraulic motor?

arrangement is 2" pump, 2" 3 way valve, elbow with 1.5" reducer, electromag and almost straight run open system.

[Vtile]

How is the motors verified to give the same RPN?
How is the flow of water measured to verify your readings from the prototype?

[deepakdange]

there is standard calibrated  rpm indicator, electromag,etc.
flow is the same (which can make variable from 0 to 26 m3/hr)
i am getting enhanced signal at amplifier output on hydraulic which is measured on the scope. viz.

5v operating(single supply) system, reference(grounding rings, etc) at 2.5v
input preamp.  INA333 with gain = 5 and standard circuit design for electromag(ref texas instruments)

batching are matched within a liter measured for 25, 50, 100, 200 liters.
motor              electric                               hydraulic

zero                1948/1934                         1948/1934
13.5m3/hr       2188/ 1690                        2450/1422

batching
25                   24.6                                  34
50                   49.8                                  71-73
100                 99.2-100.6                        142-160
200                 198-201                            276-284
slope gets changed but linear function.
is there any physical parameter affecting the system?