UNIPRO – The original Laptimer
14
Speed measurement
The speed measurement is an important feature in the Unipro Laptimer. We have made our speed
kit in a very high quality, in order to give you a precise measurement of:
•
Your speed, so you can see the effect on changes in your driving style or kart set-up
•
The tire wear
•
The lap length
•
The split points that divides the track into different sections
The measurement of speed can be done in different ways. Some Laptimers use a method where
the speed is calculated using the RPM combined with input about the gearing and wheel
circumference. Other Laptimers counts the number of pulses from a wheel sensor in a certain
amount of time, and then calculates the average speed during the period. The main disadvantages
of both methods are that they are not very precise, and have a low update frequency. These
methods are not very suitable for data logging.
Instantaneous method
The instantaneous method counts the time between pulses from a wheel sensor, and then
calculates the speed at specific instants in time. We use this method in the Unipro Laptimer. Our
wheel sensor has six pulses per wheel revolution, witch results in a very accurate speed
measurement. The total precision is 0.48% from 0 to 350 KMH combined with a very fast update
rate. The method is perfect for a real data logger and enables the PC Analyser program to do
things like a slip graph showing you if the wheel is spinning or dragging and how much!
The Slip-Distance graph shows the gearing on the left axis and the lap distance in the bottom. The
gearing is the green line. Everything above the line is the rear wheel spinning and everything
below the line is the rear wheel slipping or sliding. You can use this graph to compare your driving
style from lap to lap, and learn where it is efficient with an aggressive driving style and where it
isn’t. In order to make this graph you need a precise measurement of distance, speed and RPM.
