Patent ID: 8972208
Filing Date: 2015-03-03
Classification: G01F

Abstract:
1. A flow meter device comprising: first and second ultrasonic transmitters/receivers which are placed at an upstream side and a downstream side, respectively, in a measurement passage through which fluid flows; a transmission section that actuates the first ultrasonic transmitter/receiver to transmit a drive waveform; a reception section that detects the drive waveform propagated to the second ultrasonic transmitter/receiver, wherein the propagated drive waveform consists of a packet of waves having a plurality of zero-cross points; a time measuring section that comprises a first counter and a second counter counting at a higher speed than the first counter, wherein the first counter is activated to begin counting when the transmission section actuates the first ultrasonic transmitter/receiver, and the second counter is activated and deactivated to begin and end a counting operation repeatedly to perform multiple counting operations during a span of the wave packet such that in each of the counting operations the second counter is activated at a different one of at least some of the plurality of zero-cross points and deactivated at an end of a counting cycle of the first counter coming immediately subsequent to the corresponding one of the plurality of zero-cross points, and the time measuring section subtracts a time interval counted by the second counter during a respective at least some of the counting operations from a time interval counted by the first counter to an end of the corresponding one of the counting operations to obtain a plurality of propagation times for the propagated drive waveform; and a flow calculating section that calculates a flow rate of the fluid using an average of the plurality of propagation times obtained by the time measuring section.