Path: utzoo!utgpu!news-server.csri.toronto.edu!bonnie.concordia.ca!uunet!uunet!infonode!lester
From: lester@infonode.ingr.com (Lester Bartel)
Newsgroups: sci.electronics
Subject: Re: Digital dash (was: Inductive pickups.
Message-ID: <1991Jun3.020929.9256@infonode.ingr.com>
Date: 3 Jun 91 02:09:29 GMT
References: <1970@ole.UUCP> <1991May30.151040.50@cmkrnl.uucp> <847@newave.UUCP>
Organization: Intergraph Corp. Huntsville, AL
Lines: 24

john@newave.UUCP (John A. Weeks III) writes:

>In article <1991May30.151040.50@cmkrnl.uucp> jeh@cmkrnl.uucp writes:

>For example, I know the State Patrol in Wisconsin (a very picky state
>about traffic speed) normally does not give out speeding tickets unless
>you are going 5MPH or more over the speed limit.  I would like to set
>my cruise control at exactly 69MPH on the interstate.  With the analog
>display, I never really know exactly how fast I am going.

>Of course this assumes that a digital display is actually accurate to
>the resolution that it displays at--which is not a good assumption unless
>it has been calibrated.

The speed of your readout can vary by over 2% depending on if you have
new or wornout tires on your car.  Figure about 3/16 inch usable tread
on a tire.  Subtract 2 times this from the diameter of a new tire and
recompute the circumference.  At 60 MPH thats over 1 MPH error.  So,
even if the display is accurately calibrated, tire wear will cause some
error.  Also, there is some tire slipage depending on road material and
conditions like water or sand (or ice :-) ).
-- 
Lester Bartel			b23b!naomi!lester@ingr.com
Dazix, An Intergraph Company	uunet!ingr!b23b!naomi!lester