The G821 dual-mode liquid ultrasonic flowmeter uses a measurement method that automatically switches between the time-of-flight (TOF) measurement and the Doppler measurement. The time-of-flight method is used in scenarios where the medium is relatively uniform, and the Doppler method is used when the medium contains particles or bubbles. The installation method employs external clamp-on non-contact measurement, allowing measurement of various water media (drinking water, raw water, sewage), oils (lubricating oil, diesel, fuel oil, crude oil), as well as highly corrosive, toxic, and hazardous chemicals. It is not affected by process pressure or the conductivity of the medium, and the measurement pipe diameter can cover up to DN5000, making it an economical and efficient flow solution.

The dual-mode liquid ultrasonic flowmeter uses an automatic switching measurement method between the time-of-flight (TOF) measurement and the Doppler measurement. In scenarios where the medium is relatively homogeneous, the TOF method is used for measurement, whereas the Doppler method is used when the medium contains particles or bubbles. 

1. Time-of-Flight (TOF) Flow Measurement

The flight time (TOF) of ultrasound is related to the flow velocity of the medium in the pipe and the speed of sound. By detecting the flight time, the flow velocity of the medium in the pipe can be determined, which is then used to measure and calculate the flow rate.

2. Doppler Flow Measurement

The Doppler method utilizes the Doppler principle in acoustics. By detecting the frequency shift between the reflected sound wave and the transmitted sound wave, the flow velocity of the fluid can be determined, and subsequently the fluid flow rate can be measured. The Doppler method actually measures the velocity of particles in the fluid, and this is used as a proxy for the fluid velocity to calculate the fluid flow rate.