Gas ultrasonic flowmeter signal processing and conversion circuit

Abstract

The invention discloses a gas ultrasonic flowmeter signal processing and conversion circuit, comprising a single power supply amplifier, a gating signal generation circuit, a neutral point comparatorand a second AND gate. A comparison pulse signal for triggering a gating signal is determined according to the threshold comparison voltage, and the threshold comparison voltage is determined according to the gas pressure in a gas flowmeter, so that the threshold comparison voltage is positively correlated with the amplitude of an echo signal, and the effect of amplitude adaptation can be realized. Compared with the two excitations and peak detection of the prior art, the circuit structure and control are relatively simplified. Secondly, a first monostable trigger is used to generate a delay time of a certain length of time when a trigger signal is triggered, and a measurement channel is closed before the echo signal arrives, so that the phenomenon that interference signals enter the measurement channel to cause unnecessary influences can be avoided; and thirdly, the scheme of the invention adopts the single power supply amplifier, the neutral point voltage of the power supply, that is, Vcc/2, is used as a zero point comparison voltage, the process of supplying power by using positive and negative power supplies is not required, and the cost of circuits can be reduced.

Description

technical field [0001] The invention belongs to the technical field of ultrasonic gas flow measurement, and more specifically relates to a signal processing and conversion circuit of a gas ultrasonic flow meter. Background technique [0002] Ultrasonic flowmeter is an instrument that uses ultrasonic waves to measure flow velocity under the influence of fluid flow velocity when it propagates in fluid. When the ultrasonic wave propagates along the direction of flow, its propagation speed is equivalent to the superposition of the speed of the fluid at rest and the fluid flow velocity. The opposite is true for countercurrent propagation. Therefore, as long as the change value of the ultrasonic sound velocity is measured, the flow velocity of the fluid can be calculated, and then the flow rate can be obtained. This method is called the time difference method, and its schematic diagram is as follows figure 1 shown. [0003] Let the fluid velocity be V, the pipe diameter be D, ...

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Problems solved by technology

[0013] However, the above-mentioned echo detection circuit needs to continuously transmit two ultrasonic signals, and the peak value needs to be saved first, and then formally compared. At the same time, because of the zero-crossing detection, the comparator needs positive and negative power supplies, and the circuit and control are more complicated.

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