Red Lion LEGEND - Manual (Page 67)

COUNTER SCALING EXAMPLE: (Cont’d)
EXAMPLE #2:
A quadrature Rotary Pulse Generator that provides 100 pulses per
revolution is coupled to a feed roll that is 2.5 feet in circumference. It is
desired to read in feet with display resolution to the nearest hundredth of feet
(0.01).
In this application, the requirement is for the display to read in hundredths
of a foot. A 2.5 ft. distance equates to 250 “Display Units” (hundredths). The
“Number of Pulses” for 2.5 ft. is 100, as stated.
From the information obtained, the Total Scaling, “K
T
”, can be calculated,
using Formula #1.
K
T
= Display Units ÷ Number of Pulses = 250 ÷ 100 = 2.5
With a Total Scaling, “K
T
”, of 2.5, it can easily be seen that for every pulse
that is input, the display increments by 2.5 display units (hundredths). The
application requires resolution to the nearest hundredth of a foot. To get
higher resolution, Quadrature X4 Input Response Mode is selected. This
provides four times the resolution. Using Formula #2, and 4 for the “Number
of Count Edges”, the Remaining Scaling, “K
R
”, is calculated.
K
R
= K
T
÷ Number of Count Edges = 2.5 ÷ 4 = 0.625
At this point, it can be seen that the Remaining Scaling Factor value of
0.625 fits into the Count Scale Factor value range without losing any
significant digits or scaling it any further. Because of this, the Scale
Multiplier (SCM) factory set value of X1 is used, and 0.6250 is programmed
directly in for the Count Scale Factor, “SF”.
SF = K R ÷ SCM = 0.6250 ч 1 = 0.6250
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