Drive by wire and the wish to survice the experience.

[Chris Conlon]

At 09:49 AM 12/30/96 -0900, you wrote:

>Very inventive - but bogus (IMHO).
>
> The most common thing that goes wrong with a POT is the wiper
> connection. That'd kill both sides, and you're right back to
> no redundancy.

It would kill both sides, but your control circuit would know
*immediately* that there was a failure. Any setup, with any
number of levels of redundancy, can *still* fail. The key point
then is that you be able to *know* it's failed. An ordinary TPS
setup gives you no such luxury; this slight change does, with
almost no extra hardware. There's nothing to stop you from running
dual (triple, quad, etc) TPSs as well, depending how much
redundancy you need, as opposed to failsafe, which is what I said
this trick does. (Though personally I'd consider an LVDT on the
throttle cable as backup instead, in my experience they're more
reliable.)


>Keep thinking though...one time in ten "almost a good idea" turns
>into a GOOD idea!

Thank you for the encouragement. It already does what I wanted, namely
be able to detect sensor failure, so you can shut down, or fall back
onto some other sensor. (Like some OE apps do.) If the original
poster really needs to be able to operate normally in case of one
sensor failure, I think he's looking at *triple* sensors and a voting
scheme, or, dual sensors with this trick. (Since each sensor is then
self-diagnosing as to correct operation.)

Anyway. I don't mind having people keep me honest, and if I implied
that this design will do more than it will, I apologize.

   Chris C.