Hi Fred,
I just looked up your Mitchell Ammeter. I noted that they specify a shunt for
it. The shunt is a resistor and will by Ohms law (E=I/R) output a voltage that
is proportional to the amps passing thru it. At full current (45 Amps) it will
deliver a known voltage (usually 50 millivolts). The meter in the panel is
actually reading volts and the shunt is mounted in the engine bay. Since the
meter is +/- amps, it is designed to go in the lead right at the battery. That
way you will see negative amps if the alternator is off line or if there is
a power requirement in excess of what the alternator can deliver. You will
also see positive amps when the alternator is charging the battery typically
after
engine start. Mostly you will see zero amps showing there is no current
flow into or out of the battery since it is fully charged and the alternator is
producing the needed electricity for everything that is turned on. This is
as Frans described in the other thread.
You can install another Mitchell shunt in the wire that is the output of the
alternator.
Using a switch you can switch the meter between the two shunts. The
second shunt would give you the ability to view the output of the alternator.
That way you can see just how many amps the alternator is producing to keep
the battery charged and to power everything you have turned on.
It appears you have a Dynon EFIS. Most EFIS have engine monitoring
capabilities.
They usually use a Hall Effect ammeter which measures the magnetic field around
a wire carrying current to determine how many amps are being conducted in
the wire. This is just a different way to measure amps. If you didn't want
to use the Mitchell ammeter, you can measure amps using the Dynon.
In our Europa, we have two Hall Effect sensors. One is on the battery lead to
measure amps in and out of the battery. The other is on the output of the Rotax
alternator. They are switched by a toggle switch. Usually I just monitor
the amps into and out of the battery. But I will occasionally see just how many
amps I'm asking the Rotax alternator to deliver to assure I'm not exceeding
its capability.
Hope this helps.
Jim Butcher
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=417221#417221
|