On 15/02/2019 09:46, The Natural Philosopher wrote:
On 15/02/2019 09:13, Harry Bloomfield wrote:
I expect the standard traffic car is equipped with just the same
system has our cars have - pulse taken from the ABS of one wheel, then
electronics feeding a stepper motor, except their systems will be set
to display the true speed to ± 1 mph.

Yes. MOST cars today seem to use that system,

I have a speedo display driven from the OBD2
https://www.ebay.co.uk/itm/Car-Head-Up-Display-OBD2-II-HUD-Projector-Speedometer-MPH-KM-h-Speed-Warning-CO/362480289696

It has an ajustment for accuracy, by default that is +8%, and very much
the same as the car's speedo. Setting it to be ±0 gives a speed reading
that's consistent with both a handheld GPS and my phone GPS.


IIRC my jaguar speedos were spot on the money +- tyre wear.

In fact it went beyond that as well - the temeperature gauge was always
once warmed up EXACTLY in the dial ceter even when the warning lights
for overheating gearox came on!


I'd question ABS from ONE wheel. More likely a pair to allow for
cornering etc.





--
djc

(–€Ì¿Ä¹Ì¯–€Ì¿ Ì¿)
No low-hanging fruit, just a lot of small berries up a tall tree.