Chapter 3. Programming Site Data
26 Transport® Model PT878 Portable Liquid Flowmeter User’s Manual
3.2.1 Parameters for Special Transducers
Note: The factory will supply the information required below with the
transducers.
3. The prompt asks for the transducer frequency, to transmit a signal at a
frequency to which the transducer can respond.
a. From the Transducer prompt, press the [T] key to reach the
Frequency prompt, and press
[ENTER].
b. A drop-down list of five frequencies opens, ranging from 0.50 to
4.00 MHz. Scroll to the desired frequency, and press
[ENTER].
4. The next prompt asks for Tw, the time delay. This parameter is actually
the time the transducer signal spends travelling through the transducer
and cable. The PT878 calculates the flow rate from the upstream and
downstream transit times in the fluid, so the Tw (time delay) must be
subtracted out for an accurate measurement. The factory supplies the
time delay on a sheet of paper inside the transducer case.
a. From the Frequency prompt, press the [X] key to reach the Tw
prompt, and press
[ENTER].
b. Use the numeric keys to enter the GE-supplied time delay and press
[ENTER].
The program now varies, depending on whether you have selected a wetted
or a clamp-on transducer.
• If you have selected a special wetted transducer, proceed to
Confirming Entries on page 30.
• Special clamp-on transducers require three more inputs: wedge
angle, wedge temperature, and wedge soundspeed.
5. When calculating the flow rate, the PT878 must take into account the
wedge angle, the angle of the ultrasonic transmission.
a. From the Tw prompt, press the [T] key to reach the Wedge Angle
prompt, and press
[ENTER].
b. Use the numeric keys to enter the factory-supplied wedge angle (in
degrees) and press
[ENTER].
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