>Bob,
>Thank you for your answers. There was one more question I forgot to ask: I've
>been told that a good place to hook up the engine hour meter is to the
>charging side of the alternator - that way the hour meter only works when the
>engine is running (assuming the alternator is charging!).If this is the case,
>where would I connect the hour meter on your Z3? Would I need an inline
>Diode?
Hour meters for airplanes run on 10-15 vdc. The raw output
from your alternator is AC voltage. I've seen the technique
you asked about accomplished with a bridge rectifier, resistor,
capacitor and sometimes a zener diode for keeping the output
voltage from becomming too high (the AC output is unregulated
and quite high at cruise RPM).
My preference is for using a single pole, double throw
oil pressure switch as a combination hour meter and low
oil pressure warning light driver. The hour meter runs
directly from the battery through a 1-3A fuse and gets
ground through the close on pressure side of the switch.
A low oil pressure warning light powers from the essential
bus (or main bus if you don't have a two-bus system)
and gets ground through the close on no pressure side
of the switch.
This system will cause the hour meter to run even if the
battery master is OFF. The low oil pressure warning serves
two purposes. In addition to the obvious function, the light
serves as a reminder to shut off the battery master switch
before leaving the airplane. Some builders include a small
buzzer in the system as a audible alert. If your airplane
has an essential-bus/main-bus architecture, then driving the
warning light from the e-bus monitors both the battery master
-and- the e-bus alternate feed switches.
A diagram describing this sytem may be downloaded from
http://www.aeroelectric.com/oilpwarn.pdf
We stock the double throw oil pressure switch as
an S710-1 Oil Pressure Switch. Not in our website
catalog yet but you can order one with a statement
in the comments box that you'd like to have an S710-1
Switch. They're $7.50 plus postage.
By the way, some browser's interface with Acrobat Reader
can be flakey. One of four machines I use will not
smoothly display a .pdf link accessed directly from
the browser. Acrobat opens and the browser reports
"document done" but the page is blank. If this happens,
use your right mouse button to click on the link an
direct your browser to "save link" to some spot on your
hard drive. After the download is completed, use Acrobat
as an independent application to open the .pdf file
directly from your hard drive.
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