Electromagnetic flowmeter measuring apparatus

Claim 1

A FLOWMETER COMPRISING A CONDUIT FOR FLOWING FLUID, ELECTROMAGNETIC MEANS PROVIDING A MAGNETIC FIELD TRANSVERSE TO SAID CONDUIT, MEANS SUPPLYING ALTERNATING CURRENT TO SAID ELECTRONMAGNETIC MEANS, ELECTRODES EXPOSED TO FLUID FLOWING THROUGH SAID CONDUIT AND LOCATED ON A LINE EXTENDING TRANSVERSELY THROUGH SAID FIELD TO PICK UP SIGNALS GENERATED BY FLOW OF FLUID THROUGH SAID FIELD, MEANS PROVIDING AN INPUT CIRCUIT, CONNECTIONS FORM SAID ELECTRODES TO PROVIDE VARIABLE ALTERNATING SIGNALS THEREFROM TO SAID INPUT CIRCUIT, A VARIABLE FREQUENCY PULSE GENERATOR, MEANS RESPONSIVE TO OUTPUT SIGNALS FROM SAID INPUT CIRCUIT TO CONTROL THE FREQUENCY OF FREQUENCY SIGNAL BY SAID GENERATOR, MEANS PROVIDING A REFERENCE SIGNAL HAVING THE FREQUENCY OF SAID CURRENT, MEANS RESPONSIVE TO PULSES PRODUCED BY SAID GENERATOR TO SAMPLE SAID REFERENCE SIGNAL AT THE FREQUENCY OF SAID PULSES TO PRODUCE VARIABLE PULSES OF CONSTANT DURATION EACH OF WHICH HAS AN AMPLITUDE APPROXIMATELY PROPORTIONAL TO THE AMPLITUDE OF SAID REFERENCE SIGNAL AT THE TIME OF SAMPLING, SAID PULSES HAVING A FREQUENCY CONSIDERABLY EXCEEDING THAT OF CHANGES OF SAID REFERENCE SIGNAL, MEANS SMOOTHING SAID VARIABLE PULSES AND PROVIDING TO SAID CIRCUIT A SECOND SIGNAL IN PHASE WITH BUT OPPOSING SAID VARIABLE SIGNAL TO EFFECT SUBSTANTIAL NULLING OF SAID VARIABLE SIGNAL AT THE OUTPUT OF SAID CIRCUIT, AND MEANS COUNTING THE PULSES PRODUCED BY SAID GENERATOR.