4-24
1010GCNFM-3C
Section 4
4.4.6 THE NUMBER INDEX MENU CELL
Selecting the Spacing Offset allows the flowmeter to calculate the Number Index. The Number Index
establishes the spacing between a pair of transducers. You cannot override this recommendation. To
complete the transducer installation, you must accept the Number Index by mounting the transducer at
that point on your spacer bar or mounting track. Initially, the flowmeter bases its Number Index selection
on the pipe diameter and estimated liquid sonic velocity (Vs) you entered in the Gas Parameters menu.
When you invoke the [Install Completed?] routine, the flowmeter actually measures the gas sonic veloc-
ity (Vs). In some cases, it may prompt you to re-space the transducers to another number index.
4.4.7 THE Ltn MENU CELL
This view only menu cell shows the distance in inches or millimeters between the front faces of the
transducers along the axis of the pipe. If you are mounting the transducers without a track or spacer bar,
you have to space them according to this value (see Section 5 for details). Note that Ltn may be a
negative number for direct mount on very small pipes where the transducer spacing overlaps.
4.4.8 HOW TO USE [INSTALL COMPLETED?]
Use the [Install Completed?] menu cell to inform the flowmeter that you have mounted the transducers
according to the selected mode and spacing requirements and are ready to start operation.
To start the [Install Completed?] routine for an original installation:
z Select [Dual Path Flow] and press the <Right Arrow>.
z Press <Down Arrow> and scroll to the [Pick/Install Xdcr] menu cell. Press <Right Arrow>.
z Install transducers as required (refer to Section 5 for procedures).
NOTES
z Mount the transducers using the selected mode (direct or reflect). Please refer to the
transducer mounting procedures detailed in Section 5.
z When using a mounting track or a spacer bar in reflect mode, locate the first trans-
ducer at the Reference Index and the second transducer at the recommended Number
Index.
z If you are mounting the transducers independently, you must use the recommended
distance; Ltn to space the transducers.
z You must use the proper sonic coupling compound. See “Recommended Sonic Coupling
Compounds” in Section 6 for appropriate type and part number.
z The pipe must be pressurized to the minimum gas pressure required for operation.
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