Red Lion LEGEND - Manual (Page 64)

calculated. The Total Scaling, denoted as “K
T
”, is simply the total amount of
scaling required for the Process. It is obtained by dividing the Display Units by
the Number of Pulses as shown in Formula #1 below.
FORMULA #1: K T = Display Units
¸
Number of Pulses
WHERE:
K
T
= Total Scaling.
Display Units = The number of desired units (revolutions, feet, 10ths
of feet, meters, etc.) that would be acquired after the Number of
Pulses has occurred.
Number of Pulses = The Number of pulses required to achieve the
number of Display Units.
For the preceding example, the Total Scaling, “K
T
”, is calculated by plugging
in 2 and 48 in the formula:
K
T
= 2 ¸ 48 = 0.041667
As previously stated, the Total Scaling, “K
T
”, is the combination of the Count
Scale Factor, Scale Multiplier, and Number of Count edges. In many applications
the Total Scaling, “K
T
”, can be programmed directly into the Count Scale Factor,
“SF”, in which case the Scale Multiplier and Number of Count Edges can be left
at the factory settings of X1.
In some applications, more display resolution may be required. When the
Total Scaling (K
T
) is greater than 1.0000 and only one edge per count pulse is
used, there may not be enough display resolution.
Example: With a Total Scaling of 2.000, when an input pulse is generated, the
display increments by 2. If the display units are in feet, when 3 feet have gone
by, the display still reads 2. It will not increment again until 4 feet have been
accumulated. With this amount of display resolution it would be impossible to
set the Preset and have the output respond at odd feet intervals (1, 3, 5, etc.). To
increase resolution, the Number of Count edges must be increased. This can be
achieved by selecting the CT+DIRX2 mode (Count plus direction times 2) in
the Program Count Module or by selecting the QUAD X4 mode, if quadrature
counting is being used. If enough resolution still has not been attained, more
input pulses need to be generated per display unit.
The amount of resolution required varies depending on the particular
application. In cut-to-length applications, a high amount of resolution is often
necessary. However, in totalizing applications, display resolution may not be
important. It should be noted that whenever the number of count edges is
increased to 2 or 4, the maximum count frequency decreases. (See
Specifications for maximum count frequency).
Note: When using 2 or 4 edge counting for length sensor, on/off duty cycle must
be 50% to maintain max. accuracy (mag. pickup will not work).
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