Measuring Method of S.H.Meters. Ultrasonic Water Meter
The ultrasonic water meter is composed of an ultrasonic probe, signal processing unit, display unit, and ultrasonic flow sensor.
The ultrasonic flow sensor is an important component of an ultrasonic water meter. It is mainly composed of three parts: an ultrasonic transducer, an electronic circuit, a flow display, and an accumulation system. So how does the ultrasonic flow sensor work as the core component of the ultrasonic water meter?
The working principle of the ultrasonic flow sensor: the ultrasonic transmitting transducer converts electrical energy into ultrasonic energy and transmits it into the measured fluid. The ultrasonic signal received by the receiver is amplified by the electronic circuit and converted into an electrical signal representing the flow for display. and totalizing instruments for display and calculation. In this way, the detection and display of the flow are realized. According to the principle of signal detection, the current ultrasonic flow sensor can be mainly divided into beam shift method, Doppler method, noise method, correlation method, velocity difference method (direct time difference method, time difference method, phase difference method, frequency difference method) and other types, their characteristics are as follows
The ultrasonic water meter adopts the time difference method to measure the flow, that is, install an ultrasonic transducer on the upstream and downstream of the measurement channel (pipe section) for mutual transmission and reception of ultrasonic signals.
1. Beam offset method: using the propagation direction of the ultrasonic beam in the fluid to shift with the change of the fluid flow velocity to reflect the fluid flow velocity. When the flow velocity is low, the sensitivity is very low and the applicability is not great.
2. Doppler method: Using the principle of acoustic Doppler, the fluid flow rate is determined by measuring the Doppler frequency shift of the ultrasonic wave scattered by the scatterer in the inhomogeneous fluid. It is suitable for the flow measurement of fluids containing suspended particles and bubbles.
3. Noise method: Utilize the principle that the noise generated when the fluid flows in the water supply pipeline is related to the fluid flow velocity, and then express the flow velocity or flow value by detecting the noise. The method is simple, and the equipment is cheap, but the accuracy is low.
4. Correlation method: Use related technologies to measure flow. In principle, the measurement accuracy of this method has nothing to do with the sound velocity in the fluid, so it has nothing to do with the fluid temperature, concentration, etc., so the measurement accuracy is high and the application range is wide. But the correlator is expensive and the circuit is more complicated.
5. Velocity difference method: the basic principle is to reflect the flow velocity of the fluid by measuring the difference in velocity between the forward and countercurrent propagation of ultrasonic pulses, so it is also collectively referred to as the propagation velocity difference method. Among them, the frequency difference method and the time difference method overcome the error caused by the change of sound velocity with the temperature of the fluid and have high accuracy, so they are widely used.
The ultrasonic water meter of S.H.Meters adopts the time difference method to measure the flow rate, that is, install an ultrasonic transducer on the upstream and downstream of the measurement channel (pipe section) for mutual transmission and reception of ultrasonic signals.
Due to the superimposition of the ultrasonic signal and the water flow signal, the propagation speed of the sound wave is different in the forward flow and the upstream flow, so the running time of the ultrasonic signal emitted by different transducers in the water is different, and the fluid flow can be calculated by measuring the time difference. The flow rate, and then converted into the flow, so as to achieve flow measurement.
There are two transducers on the top of the flow tube. Transducer A transmits an ultrasonic signal to transducer B (downstream), while transducer B transmits an ultrasonic signal to transducer A (countercurrent). The countercurrent ultrasonic signal forms a certain time difference during the transmission process. In the case of the calibrated pipe diameter cross-sectional area and the standard measuring pipe length, the flow rate of the meter is calculated by the calculation chip on the integrator.