Red Lion LEGEND - Manual (Page 52)

COUNTER SCALING EXAMPLE:
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 will equate to 250 “Display Units” (hundredths).
The “Number of Pulses” for 2.5 ft. is 100, as stated.
From the information obtained, the Total Scaling Factor, “K
T
”, can be
calculated, using Formula #1.
K
T
= Display Units ¸ Number of Pulses = 250 ¸ 100 = 2.5
With a Total Scaling Factor, “K
T
”, of 2.5, it can easily be seen that for every
pulse that is input, the display will increment 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 will
provide 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 will fit into the 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
Scale Factor, “SF”.
SF = K R
¸ SCM = 0.6250 ¸ 1 = 0.6250
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