Red Lion GEMINI 52 - Manual (Page 23)

GEMINI 5200 PROGRAMMING EXAMPLE - SPEED RATIO
A paper towel manufacturer needs to maintain a tight control on the speed
relationship of two rollers. Two outputs are needed to signal when the speed
relationship of the rolls are out of the operating “safe zone”. A 72 tooth gear is
mounted on each of the rolls. Two LMPC’s are used to sense the gear teeth. Each
of the rolls have a circumference of 2 feet.
The Gemini 5200 can fulfill all the requirements of the system. The Gemini
5200 can provide an indication of the speed relationship, and can also provide a
Feet per Minute indication of the speed at which each of the rolls are running.
The system can be set-up so that the speed relationship is given as a speed ratio
or draw. After programming, only the Presets will have to be changed. In this
programming example, Display C will be set-up to indicate speed ratio, A/B.
SCALING THE RATE CHANNELS
Since both of the rolls have the same circumference and have gears with the
same number of teeth, the scaling parameters obtained will apply to both Rate
channels A & B.
The unit of display for the rate channels will be in feet. From the information
given, 72 pulses will be provided for 2 “Display Units” (feet) of linear web travel.
Utilizing the formulas and procedure in Appendix “F”, we obtain the Total
Scaling Factor required, “K
T
”.
K
T
= Display Units/Number of Pulses
K
T
= 2/72 = 0.0277777
To provide maximum conversion accuracy, a Scale Multiplier value of 0.01 is
chosentogivethelargestnumberofsignificantdigitspossiblefortheScaleFactor.
SF = K
T
/SCM
SF = 0.027777/0.01 = 2.7778
The Rate A & Rate B Scale Factors will be programmed for 2.7778 and the
corresponding Scale Multipliers will be programmed for 0.01.
The final scaling parameter that needs to be selected is the “Rate Conversion
Factors” for both of the Rate channels. To achieve rate in Feet Per Minute, the
“Rate Conversion Factor”, Rate Per Minute is selected.
-21-