Abstract: A magnetic excitation circuit is used as a circuit for providing a magnetic excitation electric current based on a magnetic excitation power supply voltage to a magnetic excitation coil of an electromagnetic flow meter. The magnetic excitation circuit includes four voltage storing circuits that store and output a driving voltage that is charged by a common driving voltage. The voltage storing circuits are connected respectively between the control terminals and the output terminals of four switching elements. When the four switching elements are turned ON in relation to a positive interval or a negative interval, the four switching elements operate by the driving voltages that are outputted from the respective voltage storing circuits.

Abstract: In a signal amplifying circuit, a flow rate signal, inputted between flow rate signal input terminals of a connector, is inputted into one input terminal and the other input terminal of an instrumentation amplifier through resistive elements and subjected to differential amplification. The amplified output signal thereof is outputted to a sample hold circuit through a coupling capacitor. The flow rate signals, inputted between the flow rate signal input terminals, are buffered by buffer amplifiers, and output signals thereof are outputted to a fault detecting circuit. An interconnection, which connects one of the flow rate signal input terminals and a non-inverting input terminal of one of the buffer amplifiers, is guarded by a guard ring pattern. An interconnection, which connects the other one of the flow rate signal input terminals and a non-inverting input terminal of the other one of the buffer amplifiers, is guarded by another guard ring pattern.

Abstract: In a signal amplifying circuit, a flow rate signal, inputted between flow rate signal input terminals of a connector, is inputted into one input terminal and the other input terminal of an instrumentation amplifier through resistive elements and subjected to differential amplification. The amplified output signal thereof is outputted to a sample hold circuit through a coupling capacitor. The flow rate signals, inputted between the flow rate signal input terminals, are buffered by buffer amplifiers, and output signals thereof are outputted to a fault detecting circuit. An interconnection, which connects one of the flow rate signal input terminals and a non-inverting input terminal of one of the buffer amplifiers, is guarded by a guard ring pattern. An interconnection, which connects the other one of the flow rate signal input terminals and a non-inverting input terminal of the other one of the buffer amplifiers, is guarded by another guard ring pattern.

Abstract: A magnetic excitation circuit is used as a circuit for providing a magnetic excitation electric current based on a magnetic excitation power supply voltage to a magnetic excitation coil of an electromagnetic flow meter. The magnetic excitation circuit includes four voltage storing circuits that store and output a driving voltage that is charged by a common driving voltage. The voltage storing circuits are connected respectively between the control terminals and the output terminals of four switching elements. When the four switching elements are turned ON in relation to a positive interval or a negative interval, the four switching elements operate by the driving voltages that are outputted from the respective voltage storing circuits.