Peter2 wrote in message
...

"N_Cook" wrote in message
...
Inhibits engaging overdrive if too slow a gear wheel or in this case
broken
wires to the sensor. Looks as though transmission fluid makes the wiring
sleeving go hard and brittle then vibration completes the job. No I
don't
know what its from , built into a 3/8 UNF stud though so localises it a
bit
I suppose .
Is the system passive or active.? Magnet as a pole piece inside a coil
probably, 330 ohm, 60nH. Spinning a steel cog in a drill , passive
output
is
about 10mV sineish pk-pk 5mm from gear and about 100mV if 3mm from the
gear.
But also a lot of EMI from the drill motor so are these things used
actively
?



From what make and model vehicle? And yes, they are active, feeding an
amplifier and pulse shaper to provide a final RPM value to the TCM.



I was not told what its from. Googling I only found references to overdrive
inhibitor switches not tachometer type sensors. So a standing 12V across
them ?