Speedometer Calibration
Speedometer calibration is the process of adjusting speedometers to match industry standards of precision for measurements of speed. Accuracy of a speedometer is important, both in order to help car owners drive safely within legal speed limits and also because the speedometer often works in conjunction with the car's odometer. Besides the safety hazards, an inaccurate speedometer can also result in an expensive ticket that will increase insurance costs.
Speedometer calibrators use electronic signals to measure the output of a speedometer; this measurement is then compared to established standards. If there is a difference between the instrument reading and the accepted standard of accuracy, the instrument can be tuned in order to provide to the correct speed measurement. This process makes the speedometer readings more exact.
As with most electronic instrumentation, speedometers should be calibrated regularly to ensure proper performance. As a speedometer becomes older, more frequent calibration may be required. Aftermarket modifications to the car, such as new wheels with a different size diameter, can also result in erroneous readings on the speedometer.