Azbil Corporation

Ichirou Mitsutake

Taka Inoue

Gain switching is performed by a DC amplifying circuit. The DC amplifying circuit is provided with individual gain generating circuits and a gain selecting circuit, and saturation preventing circuits are provided in earlier stages than the individual gain generating circuits. The individual gain generating circuit generates a gain G, the individual gain generating circuit generates a gain G(where G&#x3e;G), and the individual gain generating circuit generates a gain G(where G&#x3e;G). The gain selecting circuit selects, as a used gain generating circuit, one of the individual gain generating circuits, and sends the output thereof to an A/D converting circuit in a later stage. A gain switching instruction is sent to the DC amplifying circuit, which controls the enabling/disabling of the saturation preventing operations of the saturation preventing circuits and the selecting operation for the gain selecting circuit, to prevent the occurrence of saturation in the individual gain generating circuits that generate higher gains than the gain generated by the used gain generating circuit.

Electromagnetic flow meter

A noise eliminating circuit is provided between a sample hold portion and an A/D converting portion. In the noise eliminating circuit, a DC flow rate signal is sent from the sample hold portion through a buffer to one input terminal of an operational amplifier as a first input signal, and through a high-pass filter and a buffer to the other input terminal of the operational amplifier as a second input signal. The high-pass filter passes, as a noise component, a signal of higher than a specific frequency included in the DC flow rate signal. The operational amplifier calculates the difference between the first input signal (the flow rate signal component+the noise component) and the second input signal (the noise component), and outputs this difference (the flow rate signal component) to the A/D converting portion as the DC flow rate signal.

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Tokyo, Japan

Ichirou Mitsutake