Ultrasonic flow measurement
Walking Time principle;
The walking time principle is based on the fact that a sound pulse propagates more rapidly co-current than counter-current. The difference between the time the pulse requires and the process flow is used to determine the flow rate. Hence the name walking time principle.
The sound velocity in the gas can also be used to calculate the density.
The Doppler meter relies on the frequency change that occurs when a sound pulse is reflected from a particle that is moving from or toward the sound source. This measurement principle is best applied to liquids with contaminants in the form of particles, dissolved gas, etc. As the sound reflection can come from particles which are arbitrarily above the pipe cross-section, the accuracy can be very dependent on flow profiles and the nature of the liquid.
Ultrasonic gas flow meters:
Ultrasonic gas flow meters based on the walking time principle are today recognized as gas flow meters with a large dynamic measuring range. Maintenance is also a minimum since there are no moving parts in the process medium. They are also used today as precision meters for buying and selling. This is due to the advanced technology developed for multi-beam meters. Here, the micro processor’s capabilities are used to utilize the measurement data and continuously compare each measurement probe’s signal. Through modern filter technology, the measurement accuracy can be guaranteed within 0.5% of the measured value for a measuring range of up to 1: 160