The Doppler flowmeter product has three functions: measuring average flow velocity, measuring water depth, and measuring water temperature.

Water temperature measurement: The water temperature measurement uses a temperature probe, which is not in contact with water and is tightly attached to the top of the instrument's outer packaging material. It needs to be placed at the bottom of the water for a certain period of time to reflect the actual water temperature. The purpose of measuring water temperature is to calibrate the speed of ultrasonic waves in water and correct the water level value measured by the pressure sensor.

Water depth measurement (cross-sectional area of water passage): Imported high-precision pressure sensors are used for water depth measurement, placed at the bottom of the instrument, and the sensing part of the probe is in direct contact with the water; After measuring the water depth, the cross-sectional area of the water passage can be obtained by measuring the cross-sectional shape of the channel section.

Average flow velocity measurement: The measurement of flow velocity is obtained by emitting and receiving ultrasonic wave signals through an ultrasonic probe (transducer) and performing corresponding calculation and processing. The transducer 1 emits ultrasonic signals with a frequency of f1, which are emitted from underwater to the water surface at a certain angle. After encountering suspended particles or bubbles in the water, the frequency shifts and is reflected back to the transducer at a frequency of f2

This is the Doppler shift, where the difference between f2 and f1 is the Doppler frequency difference fd. Assuming the fluid flow velocity is v and the ultrasonic velocity is c, the Doppler frequency shift fd is proportional to the fluid flow velocity v. There are a large number of impurity particles and bubbles in water, and each reflected particle corresponds to a Doppler frequency shift fd. The flow velocity can be calculated by conversion, and the average flow velocity of these large particles is also the average flow velocity of the fluid.

By measuring the average flow velocity, water level, and cross-sectional size, the cross-sectional flow rate can be determined.