A review of speedometers and the criteria to be considered before accepting ‘frozen’ readings

More information

Main author

Goddard, C.

Co-Authors

Price, D.

Type of media

PDF

Publication type

Lecture

Publication year

2013

Publisher

22. EVU Conference, Florence

Citation

Goddard, C.: A review of speedometers and the criteria to be considered before accepting ‘frozen’ readings and other marks

EVU 2013 Florence GoddardVarious mechanisms have been used to drive speedometers and other instrument gauges. This paper reviews the mechanisms used; in particular stepper motors which have become the most common type in the last decade or so. Stepper motors require power to drive the needle to any indicated position, including to return it to zero. Hence if power to the instrument is lost as a result of a collision there is no power to move the needle and it should be left at the reading shown at the moment the power was lost. However, not all stepper motor instruments are the same and before accepting the reading a number of criteria need to be considered to give a level of confidence in the result.