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There are two important ultrasonic measurement techniques: the Doppler measurement technique and the ultrasonic delay time flow meter. A special feature of this measurement technique is that the amount flowing through the pipe can be measured from outside. These so-called clamp-on flow meters are ideally suited for temporary measurements but are sometimes also used for permanent installations.
Doppler measurement technique
Each doppler flow meter has two transducers that are controlled by a flow computer. One of the transducers is a transmitter (it sends an ultrasonic sound with a certain frequency), the other is a receiver. The transmitter sends the signal at an angle into the pipe. After this, the sound is reflected by particles and air bubbles in the liquid. Because of this reflecting the frequency of the sound changes, which is called the doppler effect. When the flow changes, the receiver will receive a different frequency, after which the computer can calculate the flow.
Ultrasonic transit time difference flowmeter
Sound that is sent along with a flowing medium comes faster on the other side than the sound that is sent against the current. This transit time difference is proportional to the speed of the medium (this can be a liquid or gas). The most important advantages are:
- No moving parts
- Straight through, obstruction- and pressure-free passage
- Can measure zero-flow
- Measuring principle independent of pressure, temperature, viscosity, etc.
- Reasonable to good accuracy (application and instrument dependent)
In addition to the flow measurement, this instrument also measures the speed of sound in the medium. This speed can be used together with pressure and temperature to obtain an indication of the density and / or average molecular weight.
Nowadays, there are also multi-channel ultrasonic flow meters in addition to the two-channel flow differential. Within the Teesing program we find 1-, 3-, 4-, 15- and 32-channel ultrasonic flowmeters.
- Doppler measuring technique
- Transit time difference flowmeter
- Certain multi-channel transit time difference flow meters can be used for calibrated measurements
Ultrasonic flowmeter documentation
Metering - gas applications
Metering - liquid applications
Process - gas applications
Process - liquid applications