US 2003/0209083 A1Published application

Flow meter

AssigneeMatsushita Electric Industrial Co., Ltd.

InventorsYuji Nakabayashi, Shuji Abe

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Abstract

An input unit for receiving a signal from an oscillator corresponds to an ultrasonic wave received by the oscillator has an input impedance significantly smaller than an impedance of an inter-electrode capacitance in the oscillator. This arrangement allows the delay of timing of the received wave to be influenced by a change in the input impedance of the input unit than by a change in the impedance of the oscillator. Since the influence of the change in the impedance of the oscillator against the delay of timing of the received wave is reduced, a flow meter can measure a propagation duration of the ultrasonic wave accurately. More specifically, the flow meter can measure the propagation duration accurately regardless of a change of the inter-electrode capacitance of the oscillator by temperature, thus measuring a flow rate of fluid correctly.

Claims11

Dependent claims

A flow meter comprising:

first and second oscillators provided at a fluid conduit in which fluid flows, for transmitting and receiving an ultrasonic wave;
a switching unit for switching the transmitting and receiving of the ultrasonic wave between the first and second oscillators;
an input unit having an input impedance smaller than respective impedances of the first and second oscillators and arranged for receiving, from the first and second oscillators, a signal corresponding to the ultrasonic wave received by the first and second oscillator;
a received-wave detector for detecting a reception of the ultrasonic wave according to a signal from the input unit;
a driver for driving the first and second oscillators to transmit the ultrasonic wave;
a time counter for counting a propagation duration of the ultrasonic wave between the first and second oscillators;
and
a flow calculator for calculating a flow rate of the fluid from the counted propagation duration.

5 more elements

Dependencies are inferred from the claim text.