What is the difference in the principle of the same kind of ultrasonic weather sensor?

Piezoelectric ceramics or magnetostrictive materials can obtain high-power ultrasonic waves under the action of high-voltage narrow pulses, which can be focused, and can be used for welding integrated circuits and plastics. After the ultrasonic wave is focused, it has good directivity. When ultrasonic wind vane sensor encounters the interface between two media, it can produce obvious reflection and refraction phenomena, which is similar to light waves.

When the ultrasonic transmitter and receiver are placed on both sides of the measured object, this type is called transmission type. The transmissive type can be used for remote control, anti-theft alarm, proximity switch, etc. The ultrasonic transmitter and receiver are placed on the same side of the reflective type, which can be used for proximity switches, distance measurement, liquid or material level measurement, metal flaw detection, and thickness measurement.

1. The principle of flow measurement by time difference method

Install two pairs of ultrasonic transmitting and receiving probes (F1, T1) and (F2, T2) at a certain distance upstream and downstream of the pipeline to be tested. Among them, the ultrasonic waves of F1 and T1 propagate downstream, and the ultrasonic waves of F2 and T2 It is transmitted against the current. Due to the difference in the propagation speed of the two ultrasonic waves in the liquid, the average speed and flow rate of the ultrasonic transducer sensor can be obtained by measuring the time difference Dt of the ultrasonic propagation on the two receiving probes.

2. The principle of flow measurement by frequency difference method

F1 and F2 are identical ultrasonic probes, ultrasonic wind sensors are installed on the outside of the pipe wall and used as ultrasonic transmitters and receivers alternately under the control of electronic switches. First, F1 emits * ultrasonic pulse, which is received by F2 through the tube wall, fluid and the other side of the tube wall. After this signal is amplified, it triggers the driving circuit of F1 again, causing F1 to emit a second acoustic pulse. Immediately afterwards, F2 emits ultrasonic pulses, and F1 is used as a receiver, and the pulse repetition frequency of F1 can be measured as f1. In the same way, the pulse repetition frequency of F2 can be measured as f2. The frequency difference D f between the downstream emission frequency f1 and the upstream emission frequency f 2 is proportional to the measured flow velocity v.