Panametrics Sentinel LCT, Руководство пользователя

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Chapter 1. Features and Capabilities
4 Sentinel LNG User’s Manual
1.2.1 Transit-Time Method
The transit time technique uses a pair of transducers, with each transducer alternately sending and receiving coded
ultrasonic signals through the fluid. Figure 2 below shows the paths used in the
Sentinel LNG
. When the fluid is flowing,
signal transit time in the downstream direction is shorter than in the upstream direction; the difference between
these transit times is proportional to the flow velocity. The
Sentinel LNG
measures this very small time difference and,
using various digital signal processing techniques combined with programmed pipe parameters, determines the
flow rate and direction.
Figure 2: Path Configuration
1.2.2 Transducers
When in a transmit cycle, transducers convert electrical energy into ultrasonic pulses and then convert the ultrasonic
pulses back to electrical energy when in a receive cycle. In other words, they act like loudspeakers when transmitting
the signal and like microphones when receiving it. They perform the actual data transmission and collection, thus
interrogating the flow.