For RPM the formula for finding the scaling factor Is:
60
PPR = Scaling Factor
Suppose you have a 72 ppr gear. The formula reads:
Scaling Factor = 60 = 5
72 6
For GPM the formula for finding the scaling factor is:
60
PPG = Scaling Factor
where PPG = Pulses Per Gallon
Suppose you have a gear operating at 140 PPG. The formula reads:
Scaling Factor = 60
= 3
140 7
For FPM the formula for finding the scaling factor Is:
60 x π x D’
PPR = Scaling Factor
Suppose you are monitoring the speed of a moving conveyor belt. To calculate the scaling factor,
you would need to know the diameter (In feet) of the roller to which the gear is attached and the
thickness of the belt (multiplied by 2). If the diameter of the roller is 1 ft. 10 Inches and the thickness
of the belt Is 1inch (x2). and the gear is 48 ppr. then the formula reads:
Sealing Factor = 60 x 3.1416* x 2’ = 7.8512
48 1
* π always = 3.1416
You can improve the accuracy of the scaling factor by manipulating the fraction in a way that uses
the full 4 1/2 digits that can be entered on the Display. In this example the two 4 1/2 digit scaling
factors are used to scale the channel with 5 digits of accuracy.
7.8512 = 7.8512 x 10000 = 78512 ÷ 4 = 19628
1 1 10000 10000 4 2500
For IPM; YPM; IPS; and FPS the formulas for finding the scaling factor are:
IPM: 60 x π x D” = SF YPM: 60 x π x D’ = SF
PPR PPR x 3
IPS: π x D” = SF FPS: π x D’ = SF
PPR PPR
Where
D’ = diameter in feet
D” = diameter in inches
SF = scaling factor
Note: In some applications the shaft’s speed you want to read may not be accessible. You may
need to mount the gear and sensor on a shaft whose speed is proportional to but not the same as
the one you want to read. In such cases, you will need to determine the ratio of speeds. For
example, if the shaft to which you have mounted the gear and sensor makes three rotations for
every single rotation of the shaft you want to read, then you must divide the scaling factor by 3.
5
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