Ira,
Great investigative work as usual...
It must be the coriolis effect.
Westach has always been great about for their flexibility. A real
credit goes to them also.
I would have had them change the part number to 720-12IRA
Bud
----- Original Message -----
From: rampil<mailto:ira.rampil@gmail.com>
To: europa-list@matronics.com<mailto:europa-list@matronics.com>
Sent: Thursday, December 06, 2007 12:29 PM
Subject: Europa-List: Prop Tach Sender
<ira.rampil@gmail.com<mailto:ira.rampil@gmail.com>>
Greetings All,
A tech tidbit for the group.
I have been investigating why my prop tach sensor doesn't work and
finally discovered the solution, which I put forth for other who may
wind up in this boat.
I have an AirMaster prop and a Blue Mountain EFIS. So far there is no
way for the BMA to read the engine RPM signal (although that may
change soon). The AirMaster hub has a magnet embedded in it's contact
plate for its own internal RPM sensing. Since I could not expose the
electric RPM signal, I put my own Hall effect sensor on a bracket
mounted
to the Rotax gear box of my 912uls. The sensor I used is a Westach
720-12R.
This sensor never produced a pulse train signal for the Blue Mountain
to analyze.
I finally put a scope on the probe and discovered that indeed not
pulses
were generated by a spinning prop. (I really did not want my scope
that close to the spinning prop ;-) )
It turns out that the Hall Effect sensor uses a neat integrated sensor
chip which it turns out is sensitive only to a SINGLE magnetic
polarity.
By random chance, AirMaster uses the wrong one. (North vs South, etc).
The Westach pulses just fine when I swish a different magnet past it.
It turns out that Westach can build the probe with sensitivity to the
opposite magnet face. The part number is you need this new probe
is 720-12RAM. Same price as the original 720-12R probe.
Hope this solves someone else's mystery too!
Ira N224XS
--------
Ira N224XS
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