Red Lion GEMINI 2 - Manual (Page 22)

DUAL PRESET RATE PROGRAMMING APPLICATION EXAMPLE
A typical industrial Dual preset rate indicator application would be the
speed control of a web press operation in a newspaper plant. The Gemini
2000 as pictured, is programmed to read out in feet/min. every two seconds.
The input is from the rotary pulse generator that is attached on the drive roll.
In this case, the RPG is delivering 120 pulses/rev. and the circumference of
the roll is 6.35 ft. By substituting in our formulas as shown in Appendix “E”,
the correct parameters are determined.
FORMULA [A]
PPS
=
RPM x PPR
=
1 x 120
=
2 PPS
60 sec. 60
FORMULA [B]
SCALE FACTOR
=
DESIRED READING
=
6.35
=
1.5875
PPS x SAMPLE TIME 2x2
By programming a 1.5875 Scale Factor and a 2-second sample time, the
Gemini 2000 will display the FPM of the roll every 2 seconds. If added
resolution is desired, the number of count edges could be changed to 2, and
the scale factor would become 0.7938.
The drive mechanism of the roll will react to a contact closure to increase
or decrease speed at a set rate for the duration of the closure. The 2-second
sample time with a 0.5 second closure (Time delay) at the beginning of each
sample time, will allow the web process to remain within the lower and
upper tolerances. In this application, the lower speed limit is 500 FPM and
the upper limit is 700 FPM. When time delay output termination modes are
used in the Gemini 2000, Output 1 activates when the rate is lower than
Preset 1 and Output 2 activates when the rate is higher than Preset 2. With
this in mind, Output 1 is connected to the speed increase drive and set to the
lower limit and Output 2 is set to the upper limit of the speed range. When the
rate drops below 500 FPM for the 2-second sample time, Output 1 will
activate for 0.5 seconds. Conversely, when the rate exceeds 700 FPM for the
2-second sample time, Output 2 will activate for 0.5 seconds.
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