Baker Hughes Panametrics AquaTrans AT600, User Manual

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Chapter 1. General installation instructions
2 AquaTrans™ AT600 User’s manual
1.2 Theory of operation
The AT600 flow meter uses a procedure called transit-time flow measurement. In this method, two transducers, which
are in acoustic communication with each other, serve as both ultrasonic signal generators and receivers. That is, the
second transducer can receive ultrasonic signals transmitted by the first transducer and vice versa. In operation,
each transducer functions as a transmitter, generating a certain number of acoustic pulses, and then as a receiver
for an identical number of pulses (see figure 2 and figure 3 below). The time interval between transmission and
reception of the ultrasonic signals is measured in both directions. When the liquid in the pipe is not flowing, the
transit-time downstream equals the transit-time upstream. However, when the liquid is flowing, the transit-time
downstream is less than the transit-time upstream. The difference between the downstream and upstream transit
times is proportional to the velocity of the flowing liquid and its sign indicates the direction of flow.
Figure 2: Flow and transducer paths (two traverses)
Figure 3: Flow and transducer paths (one traverse)