> In today's electronics/electriucals, unless
> something is violated in terms of rated design,
> the electronic/electric usually is rock solid once
> an "infant mortality" phase is passed...and even
> such infant mortality/initial use hase a pretty
> good reliability factor.
Problem is, it's difficult to keep instrumentation purely in the electronic
realm. The usual way of building an oil pressure sender, for example, is
something very similar to a mechanical gage movement, with a diaphragm
flexing under pressure and moving a variable resistor through a linkage.
Then there's the problem that automotive electrical systems are very harsh
environments. I can't quote the exact SAE recommendations offhand, but they
include transients in the 100's of volts for many milliseconds; and many kV
for shorter periods. Any design that doesn't adequately deal with these
issues will be unreliable.
Then there's the constant temperature cycling (150F is not at all unusual in
an enclosed car parked in the sun ... not to mention cockpit temperatures
while racing), mechanical vibration, etc.
It is of course possible to build electronics that survive in these
environments (as my employer does), but it's by no means easy or cheap.
Automotive OEMs are sensitive to every $.0001, so their units are absolutely
the cheapest thing that will outlast the warranty.
Just my $.0002
Randall
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