Atec Panametrics-Olympus-DF868 - Manual (Page 3)

GE
Sensing
Transmit
signal
Tracking
window
locked onto
receive signal
Time
Variable time
interval
Range of tracking window
Receive
signal
ATW ensures accuracy when fluid conditions change.
Flowmeter Transducers
Fluid
Flow
Ultrasonic Signal Path
Transit-time flow measurement technique
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.
The DF868 Flowmeter
Uses the Transit-Time Flow
Measurement Technique
The transit-time technique uses a pair of transducers,
with each transducer 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
velocity of the flow. The DigitalFlow DF868 measures this
time difference and uses programmed pipe parameters
to determine flow rate and direction.
Automatically Adjusts to Changing
Fluid Properties
Our unique Automatic Tracking Window™ (ATW™)
feature, standard in all DigitalFlow DF868 meters,
ensures accurate flow measurements even when fluid
properties are unknown or changing. Like the seek mode
on a car stereo, ATW dynamically sweeps the receiver
window whenever the sound speed of the fluid changes.
This powerful feature enables flow measurement when
the fluid sound speed is unknown, when it is changing
due to large temperature shifts, or when a new liquid
starts to flow in a multiproduct pipeline.
Is Built to Be Economical and
Stay Economical
To be of real value, a flowmeter must be as economical
to own and operate as it is capable in the field. Using the
latest microcircuit and manufacturing technologies, the
DigitalFlow DF868 flowmeter is built to stay in service for
many years. Completely solid state, the
DigitalFlow DF868 rarely wears out or needs servicing,
resulting in little downtime and low maintenance costs.
The DigitalFlow DF868 will continue to save money by
streamlining the measurement process and trimming
labor costs.
ATW works for both clamp-on and wetted transducer
applications by searching for a reliable ultrasonic receive
signal. It does this by varying the time between the
transmit signal and the receive signal window until the
receive signal is found. The tracking window
automatically sweeps through a range of time intervals
based on the minimum and maximum expected sound
speeds programmed by the user.
The window moves (tracks) in response to changes in the
fluid sound speed. Once the optimal signal is found, ATW
locks onto it until another large change in sound speed
occurs. When this happens, ATW returns to the seek
mode until the optimal signal is found again.