STACK ST8130 Series Road Car Display Systems
Chapter 4. Configuring the Display System
Users Guide
25
If the sensor is mounted on a driveshaft or the propshaft, set the
circumference to:
Actual wheel circumference ÷ differential ratio
-where the differential ratio is calculated as:
crownwheel (ring) teeth
÷
pinion teeth
Note: If the resulting value is less than 500mm or 20.0 inches, double
both this value and the number of pulses per revolution. This is to make
the calculated speed and distance as accurate as possible.
Set the number of pulses per revolution to the actual number of pulses
per revolution of the shaft.
Examples for 9 pinion teeth & 41 crownwheel (ring) teeth:
UK/EU
Differential ratio: 41
÷
9 = 4.55
Pulses per revolution: 4
Tyre circumference: 1800mm
Circumference = 1800
÷
4.55 = 395mm
Double the two values:
Wheel Cir (mm) = 790mm
W.S. Pulses/Rev = 8
US
Differential ratio: 41
÷
9 = 4.55
Pulses per revolution: 4
Tire circumference: 70.9 inches
Circumference = 70.9
÷
4.55 = 15.6 inches
Double the two values:
Wheel Cir(ins) = 31.2 inches
W.S. Pulses/Rev = 8