Abstract: A magnetic flowmeter includes a coil driving circuit which controls both the maximum, steady state current and the current rise time through the coils and makes them independent of the inductance of the particular coil being driven. The maximum current is set by a reference voltage derived from a common source with a second reference voltage utilized in the signal processing chain. The ratio of these reference voltages therefore remains constant and the output signal is independent of the absolute value of the common source of the two reference voltages.

Abstract: A voltage controlled oscillator (VCO) system includes a feedback loop for maintaining the linearity, temperature stability and accuracy of the VCO. The feedback loop includes means for producing a fed-back train of pulses having an amplitude equal to a reference voltage and a duty cycle proportional to the ratio of the frequency of the output of the VCO to a reference frequency. The output frequency is thereby made proportional to the input voltage times the ratio of the reference frequency to the reference voltage.

Abstract: A fullscale setting device for a magnetic flowmeter or the like receives a frequency encoded input and divides it by a mixed number having an integral part and a fractional part to produce an output. The mixed number may represent a flow rate which is taken as the fullscale setting, thereby making the fullscale setting independent of the calibration of the flowmeter.

Abstract: A magnetic flowmeter includes means for sensing the polarity of its output signal and automatically reversing its electrode leads in response to a change in polarity.

Abstract: A magnetic flowmeter having a pair of opposed pick-up electrodes equipped with ultrasonic cleaning transducers powered from an ultrasonic generator. A sequencer places the flow signal processing system in a hold state during activation of the transducers so as to eliminate interference with the flow signal.

Abstract: The internal accuracy of a magnetic flowmeter signal processing chain is preserved throughout an extended flow range by means of an automatic ranging system which automatically multiplies the gain of an amplifier in the chain as the flow rate decreases, and simultaneously divides its output to produce an essentially continuous output signal. The automatic ranging system eliminates manual range setting and is not observable from outside the system in the steady state.

Abstract: A family of magnetic flowmeters of different sizes ranging from at least as small as two inches in diameter to at least as large as twenty inches in diameter share a common low power coil driving circuit and a common signal processing circuit. The meters have coils which share proportional geometry and which have no magnetic core.

Abstract: A magnetic flowmeter system includes an automatic zeroing system for a multiple stage amplifier. The zeroing system includes a circuit for sequencing the turn-off time of the zeroing amplifiers such that the first stage zeroing amplifier is turned off before later stages, thereby reducing the effects of zeroing errors introduced when the zeroing amplifier for the first stage signal amplifier is put into a hold state.