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Electronic Ignition spark advance signal boost CORRECTION

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PostPosted: Tue Jan 09, 2018 8:34 am    Post subject: Electronic Ignition spark advance signal boost CORRECTION Reply with quote

At 07:38 PM 1/8/2018, you wrote:
--> AeroElectric-List message posted by: "Airdog77" <Airdog77(at)>


I missed this post earlier and noted your comment Re. this corrected diagram in the other thread.

I'm hoping 4-5" from the case is close enough to tie into the ground wire for pin 1 input? As I mention in the other thread, for some reason the ground wire on this unit is massive, around 12-14AWG.

Exactly what parameter is being conditioned by
the AD626?

The is a DIFFERENTIAL amplifier which offers
a larger image of the voltage presented to the
two inputs IRRESPECTIVE of the common mode
voltages. For example, you can tie the inputs
of the AD626 to the two terminals of an alternator
b-lead shunt that may be 28 volts or more ABOVE
ground and endowed with lots of trashy noise . . .
while seeking to amplify a 0-50 MILLIVOLT signal
across the shunt up to a 0-5 VOLT signal for
interpretation by the data acquisition system.

This means that where ever the (+) input of
the amplifier is tied, the (-) input is VERY
CLOSE BY. What ever the (+) input sees in terms
of voltages to be ignored, the (-) input must
see the SAME NOISE.

Can you scan a sketch of what you're attempting
to resolve with respect to wiring? What's the
sensor, where's it located, what excites
the sensor?

In all my many experiences with the AD626 and
cousins, the DISTANCE between points sampled
by the two inputs has never been more than inches
apart and usually millimeters apart conducted
to the amplifier on twisted pair of wires.

One such application had the AD626 looking at
a strain gage embedded in the core of a pitch
trim actuator attach bolt. I needed to resolve
MICROVOLTS of signal from 5 VOLTS of common
mode at the end of about 40 feet of twisted
pair that traversed the noisiest environs on
the aircraft.

This is a really capable device but unless
applied with understanding, the results will
disappoint. I'm unable to offer a considered
answer to your question without knowing more
about the physical layout of the system components.

Bob . . .

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