Talk:Air core gauge

Interesting. Is this same sort of indicator used in electronic speedometers and the like? The information on this page seems to, at worst, contradict that given on the speedometer page itself, or at least could add useful information to it if some basic parts were copied over. However, it would be foolish to do so if the speedo (and more modern tachos) use some other method, e.g. an electronic variant of the eddy current vs spring system. 193.63.174.11 (talk) 12:05, 24 March 2011 (UTC)

They're relatively rarely used for speedometers, more common for secondary gauges such as fuel or temperature, where they've been used for many years. The advantage of the air core gauge is that it doesn't measure voltage or current, but rather the ratio between two currents. If a car has simple electrics and relatively poor stabilisation of the instrument voltage, this ratio gives a more stable display.

Speedometers and tachometers have generally measured pulse frequency (some older systems did use tachogenerators), which means electronics, which means voltage stabilisation, even if only within the instrument case. So these have usually used traditional current balance meters, where a coil and magnet act against a spring. "Smart" tachometers ('80s onward) even started using stepper motors. Only recently have air core meters started to take over these roles too, probably because they are now more powerful than before and so can hold a larger needle stable against vibration. Andy Dingley (talk) 12:58, 24 March 2011 (UTC)