Chapter 2. Initial Setup
38 DigitalFlow™ XGM868i Startup Guide
2.7.1 Special Transducers
3. Scroll to the transducer Frequency (supplied by the factory) and press [Enter].
Note: The frequency is required to transmit an excitation voltage at the transducer’s natural frequency.
4. Enter the special transducer Tw (time delay) value (supplied by the factory) and press [Enter].
Tw is the time required for the transducer signal to travel through the transducer and its cable. This time delay must
be subtracted from the transit times of the upstream and downstream transducers to ensure an accurate
measurement.
2.7.2 Pipe Data
If either a standard or a special transducer is being used, the programming sequence should be rejoined at this point.
5. To select the appropriate Pipe OD Unit type from the list shown in Table 10 below, scroll to the right side of the
screen, and use the up and down arrow keys to step through the list. Press [Enter]. Then use the arrow keys to enter
the known pipe outside diameter or circumference on the left side and press [Enter].
Obtain the required information by measuring either the pipe outside diameter (OD) or circumference at the
transducer installation site. The data may also be obtained from standard pipe size tables found in Sound Speeds
and Pipe Size Data (914-004).
6. Use the arrow keys to enter the known Pipe Wall Thickness (in inches or mm) and press [Enter]. If the pipe wall
thickness is not available, look up the value in a table of standard pipe size data which can be found in the Sound
Speeds and Pipe Size Data manual (914-004).
2.7.2a Path and Axial Lengths
7. To enter the Path Length:
a. Use the [] arrow key to highlight the path length unit type at the right of the screen.Then use the [] and []
arrow keys to scroll to the desired unit type.
b. Use the [] arrow key to return to the numeric entry on the left, and enter the path length of the ultrasonic
signal. Press [Enter].
Note: If a spoolpiece was ordered with the meter, the transducer signal path length (P) and the transducer signal axial
length (L) are engraved on the flowcell and/or are included in the documentation supplied with the meter. For
on-site transducer installations, refer to Appendix C, Measuring P and L Dimensions.
Table 10: Available Pipe OD Units
English Metric
inch mm = millimeters
feet m = meters
in/PI = pipe circumference in inches mm/PI = pipe circumference in millimeters
ft/P I= pipe circumference in feet m/PI = pipe circumference in meters
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