Speedometer calibration uses electronic signals to measure the actual output of the speedometer and compare it to the established output standard that is set by the manufacturer of the vehicle. If a difference between the instrument reading and the accepted standard is determined and verified, the calibration device can tune the speedometer in order to provide the correct speed measurement.
This process makes the speedometer readings more exact and, as a result, the odometer reading more exact as well. The accuracy of speedometers is important because it ensures users they are driving within legal limits and avoiding expensive moving violations and high insurance costs, as well as other safety hazards.
As with most electronic instruments, speedometers should be calibrated regularly to ensure proper performance. In order to ensure that the torque created by the magnetic field reflects the speed of the car accurately it must be calibrated. Calibration services must take a number of factors into account concerning the machine being calibrated, such as gear rations in the drive cable, final drive ratio in the differential and the diameter of the tires.
As a speedometer becomes older, more frequent calibration may be required. Aftermarket modifications to the vehicle, such as new wheels with a different size diameter, low tire pressure, extra weight in the vehicle and environmental conditions can also result in erroneous readings on the speedometer and odometer. If aftermarket changes occur, the user must make the proper adjustments in the calculations to recalibrate the car. This can be done by manipulating that hairspring, the permanent magnet or both. Doing this will optimize the efficiency of a vehicle.