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
?

"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.

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 ?

"N_Cook" wrote in message
...
Peter2 wrote in message
...


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 ?


Your description is an inductive tachometer pickup coil... I don't think you
will find any biased with 12 volts across them either.

Peter2 wrote in message
...

"N_Cook" wrote in message
...
Peter2 wrote in message
...


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 ?


Your description is an inductive tachometer pickup coil... I don't think
you
will find any biased with 12 volts across them either.



I hope gearboxes make good Faraday screens against ignition EMI, there is no
braid screening around the signal wires though.

"N_Cook" wrote in message
...
Peter2 wrote in message
...

"N_Cook" wrote in message
...
Peter2 wrote in message
...


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 ?


Your description is an inductive tachometer pickup coil... I don't think
you
will find any biased with 12 volts across them either.



I hope gearboxes make good Faraday screens against ignition EMI, there is
no
braid screening around the signal wires though.



Generally twisted pair is used (at least on the ones that I work with), and
I've had little problems with EMI (though I do work primarily with diesel
trucks so EMI won't be ignition based at least). These same transmission
(for me) are used with gas engines however, so it appears to the designer
that EMI won't be an issue.

Used in a Land Rover