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Overdrive inhibitor sensor

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N_Cook

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Jul 24, 2011, 5:56:54 AM7/24/11
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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
?


Peter2

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Jul 24, 2011, 11:54:05 AM7/24/11
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"N_Cook" <div...@tcp.co.uk> wrote in message
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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.


N_Cook

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Jul 24, 2011, 1:39:03 PM7/24/11
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Peter2 <pet...@hipson.net> wrote in message
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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 ?


Gareth Magennis

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Jul 24, 2011, 2:59:29 PM7/24/11
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"N_Cook" <div...@tcp.co.uk> wrote in message
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I think you should ask this question in uk.rec.cars.maintenance instead.
Lots of very knowledgeable people there.

Gareth.

Peter2

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Jul 24, 2011, 6:13:40 PM7/24/11
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"N_Cook" <div...@tcp.co.uk> wrote in message
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> Peter2 <pet...@hipson.net> wrote in message
> news:j0hf6u$v12$1...@dont-email.me...
>>
>
> 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.


N_Cook

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Jul 25, 2011, 3:28:01 AM7/25/11
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Peter2 <pet...@hipson.net> wrote in message
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I hope gearboxes make good Faraday screens against ignition EMI, there is no
braid screening around the signal wires though.


Peter2

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Jul 25, 2011, 7:11:23 AM7/25/11
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"N_Cook" <div...@tcp.co.uk> wrote in message
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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.

N_Cook

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Jul 26, 2011, 3:18:57 AM7/26/11
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Used in a Land Rover


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