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From: firstname.lastname@example.org (Mike Harding)
Subject: Re: Car speed conversion error
Date: Tue, 19 Nov 2002 22:03:32 GMT
NNTP-Posting-Date: Tue, 19 Nov 2002 21:59:12 +0000 (UTC)
X-Newsreader: Forte Free Agent 1.1/32.230
On 19 Nov 2002 16:31:12 -0500, email@example.com
(Stephen H. Westin) wrote:
>firstname.lastname@example.org (Amy) writes:
>> Does anyone know what is the conversion error when an analog pulse
>> waveform from vehicle speed sensor gets converted to digital format
>> which can be processed by electronic control unit in a car? Is there
>> any standard on the tolerance for this conversion, or is it up to car
I think that analogue pulse is usually a digital one. The error
through the electronics would be next to stuff all - probably just
the tolerance of the crystal oscillator used by the micro which
measures the pulse interval. Tyre wear would probably account
for a much larger error.
>I don't think there is any standard for speedometer accuracy, so the
>market rules. Italian cars used to be famous for speedos that would
>read 10%-15% high.
There sure is in Australia. Australian Design Rules (and I
think the UK does too) require speedos to be within +/- 10%.
Which makes our tolerance of +3kph on a 100kph speed
limit before a ticket is issued an extreme example of
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