TPS Sensitivity

[Frederic Breitwieser]

>  I tried feeding an op-amp thru two different resistors, and
>and to caps at the op inputs, with resistors to bleed down
>the caps, but no luck (this is a clue to my limited electrical
>knowledge).

Actually, that's exactly what I would have done, one resistor across the +
input and the output, the - input connected to the output, and a resistor
in series with the + input and the TPS sensor, assuming its a three-lead
variable resistor connected to power, + and - (ground).  If the resistors
are of equal value, you basically made an op-amp buffer circuit.  If you
reverse the + and - inputs on the op-amp, you have an inverter.  A
capacitor, placed between the input of the op-amp (+ or - depending if you
are buffering or inverting) will smooth the input making up for "flash
spots" on the variable resistor, whereas dirt or grimies cause the input
lead to break off the resistor element.

By adjusting either resistor individually, you can increase or decrease the
gain of the op-amp, thus controlling the output swing in relationship to
the input swing.  This is beneficial if the TPS puts out 0-12V, and you
want 0-5V for example, or to swing the other way.

Anyway, I'm suprised it didn't work for you... that's pretty much what I
have designed into my untested ECM schematic.


Frederic Breitwieser
Bridgeport, CT 06606
http://www.xephic.dynip.com/

1993 Supercharged Lincoln Continental
1989 4-Door Softtop Humvee (Hummer)
2000 Buick GTP (Mid-engine track car)

---