Model CTF878 Startup Guide
3
Chapter 1.
1.1.1.2
Transducers
The transducers are like a loudspeaker and microphone system that uses ultrasonic acoustic waves to interrogate
the flow. For the CTF878, the transducers are mounted on a clamping fixture.
•
TRANSDUCERS
-
The transducers convert electrical energy into ultrasonic acoustic waves when on the transmit
end (sending sound into the pipe), and convert the ultrasonic acoustic waves back to electrical energy when on
the receive end (listening for the sound waves to arrive). In other words, they act like loudspeakers when
transmitting the signal and like microphones when receiving it.
•
CLAMPING FIXTURE
-
The clamping fixture provides mechanical support for the transducers and assures stable
alignment for accurate measurement (see Table 1-1 below and Figure 1 on page 4).
1.1.2
Theory of Operation
The CTF878 uses an ultrasonic flow pattern recognition technology called
Correlation Tag flow measurement.
Correlation Tag technology utilizes a total of four clamp-on ultrasonic transducers externally mounted on a pipe. The
transducers are arranged in two pairs–one upstream and one downstream. The upstream and downstream pairs
are each composed of one transmitter sending ultrasound in a continuous wave mode through the fluid to its
receiver, forming an upstream and downstream interrogation path. The continuous wave signal is modulated by
turbulence and local density variations that are characteristic of a moving gas. Thus, both sets of the received signal
contain a unique turbulence signature of the flowing gas. The received ultrasonic signals are demodulated and
processed through a correlation algorithm. With turbulent flow conditions, a distinct correlation peak is recorded,
which reflects the time it took for the unique turbulence signature to travel past each ultrasonic interrogation path.
Since the distance between each interrogation path is defined in the transducer set-up, the flow velocity is easily
calculated by dividing distance by the time it took for the turbulence signature to pass between each interrogation
path.
Pipe Size, O.D.
Clamping Fixture
from 6 to 8 inches
CFT-V8
from 10 to 12 inches
CFT-V12
from 14 to 30 inches
CFT-PI
Summary of Contents for CTF878
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