Baker Hughes Panametrics Sentinel LCT8, Руководство пользователя

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Chapter 1. General
information
1.1 Theory of operation
The Sentinel LCT8 measurement system uses ultrasonic
transit-time technology. A brief description of transit-time
theory follows. For more information about the theory, and
the use of Panametrics ultrasonic flow meters for measuring
flow, please refer to Ultrasonic measurements for process
control by L.C. Lynnworth (Academic Press, 1989).
1.1.1 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. 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 LCT8 measures this very small time
difference and, using various digital signal processing
techniques combined with programmed pipe parameters,
determines the flow rate and direction.
1.1.2 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.
The transducers in the
Sentinel LCT8 measurement system
were specifically designed to be replaced under normal
operating conditions. A damaged or non-functional
transducer, can be replaced without shutting down the
pipeline. Recalibration of the replacement is not necessary.
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