Reviewing The Spacing Method; How To Use The Spacing Offset - Siemens SITRANS F Operating Instructions Manual

Section 2

2.4.4 REVIEWING THE SPACING METHOD

The flow computer analyzes your transducer selection, mounting mode and pipe size to de-termine
the best way to install your transducers. It will recommend the use of either a mounting track, a spacer
bar, or independent mounting. The flow computer will list the part number of a mounting track or spacer
bar. (Note: If you select 991 Universal Transducers, this function is not provided.) If it decides upon
independent mounting, it will report the distance required between the two transducers. In this case,
you have to make sure that when you mount the transducers, the space between them equals the
length specified in the Ltn menu cell. See Section 3 for details on how to accomplish this.

2.4.5 HOW TO USE THE SPACING OFFSET

After you select the mounting method, the flow computer checks your entries for pipe size, transducer
type, etc. and then recommends a spacing offset. This is the first step in establishing the correct
distance between the transducers. Spacer bars and mounting tracks utilize number indices (i.e., pre-
determined mounting locations) to simplify transducer placement. One transducer is located at the
Reference position, while the other one is located at the Number Index position. The Number Index
cannot be directly edited. However, the Spacing Offset can be changed via its option list. Changing the
Spacing Offset will alter the reported Number Index. Maximum spacing offset provides moderately
greater signal levels but, in some cases, slightly decreased zero flow stability. (Note: This mounting
method is different for the System 991 Flowmeter.)
If the flow computer reports "Use Ltn," you have to measure the distance between the upstream and
downstream transducers. The flow computer issues the actual distance between the transducers in
inches or millimeters (See Ltn). Please consult Section 3 for details on how to use the Ltn measure-
ment. Note that, even though using Ltn does not call for the physical use of the Number Index, you can
still change the Spacing Offset to influence the strength of the transmit signal.
System 1010 uses a pair of precisely matched transducers so you can select either one for the Refer-
ence position. You must connect the Up transducer cable to the transducer mounted on the upstream
side of the mounting track. This enables the meter to display the flow direction correctly.
It is important that you note each transducer's serial number and its Index position during the original
installation because, to reinstall the flowmeter successfully, you must remount each transducer in its
original position. Transducer pairs have matching serial numbers except for the appended letters "A"
and "B." This helps you to identify each transducer.
To select a different Spacing Offset
To access to [Spacing Offset] option list press
To move the cursor to the desired offset press
To store selection press
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