Bailey Moyes 912 Dragonfly, Maintenance Manual

Page: 112 / 191

Page 111
The instrument should be secured using the mounting holes in the faceplate. Figure 4 provides the
physical dimensions of the instrument and a full-size mounting template. If the mounting template is
used, its dimensions should be verified, as paper may expand and contract with humidity.
NOTE: No special consideration must be given regarding protection from vibration. The mechanical
design of the instrument is very rugged. This is of course not true of other instruments, especially
mechanical airspeed indicators and altimeters. The instrument does not emit electrical noise that will
interfere with any radios, and can be mounted next to a radio without concern. A magnetic compass
may also be located next to the instrument if desired, with no measurable effect, on or off.
5.2 Wiring
Figure 5a & 5b illustrates all electrical connections made to the EIS. The “Detailed Wiring
Description” below provides additional information about wiring the instrument into your aircraft.
Review this material to familiarize yourself before proceeding further.
Using this figure, start the wiring process by carefully planning and
DRAWING A WIRING
DIAGRAM for your aircraft. The wiring diagram is essential in planning a successful installation.
Install the wiring, routing all wires required by the EIS to its planned location. A high-quality 22-
gauge stranded wire, 7 or 19 strands, is recommended for all connections other than those made to the
CHT and EGT probes. Solid conductor wiring is not acceptable. Thermocouple extension wire must
be used for the CHT and EGT probes to prevent the introduction of errors into these measurements.
CAUTION: Use a separate ground wires for the ignition kill switches and the remainder of the
electrical system if possible. These separate ground wires should attach to different places on the case
of the engine so that both sets of grounds could not disconnect from the engine while remaining
connected to each other. This provides additional protection for the instrument (although its internal
protection is usually more than adequate), but more importantly, protects other electronic equipment in
your airplane from potential damage. See the sheet at the back of the manual for more information.
All electrical connections are made to the EIS via two 25-pin sub-D type connectors. Pre-wired, color-
coded cables are supplied with the instrument.
1) Start by making the power and tachometer connections as illustrated in figure 7. Note that 10.5-20
Volts DC, 0.20 Amperes is required to power the instrument. The instrument includes an internal
thermally activated fuse that protects the instrument. A fuse should be used in the aircraft wiring so
that a short in the wiring external to the instrument does not cause an electrical fire. Typically a fuse up
to 5 amps may be used for this purpose, depending on the wire gauge and lengths. This fuse may be
shared with other items, such as radios and such.
2) For proper operation of the instrument, the ground (black wire) from the instrument must be
connected to the case of the engine. Since most engines are grounded to allow operation of the electric
starter, only the connection from the instrument to the negative (-) terminal of the battery must be
considered. Ideally, the ground wire for the instrument should not be shared with other electrical
devices. If other devices share the ground wire used by the instrument, use a digital voltmeter to verify
the voltage difference between the case of the EIS, and the negative terminal of the battery is less than
20 mV with all electrical devices which share this ground wire turned on.