GRT Avionics, Inc.
May 2019
Sport SX Install. Manual
18
Rev. A
•
If you should need to install you own terminals, information on how to crimp wires
is available on the EAA’s “Hints for Homebuilders” website, as well as written
information in the publications listed in section
2-9: For More Information
.
•
A wiring diagram is provided in the
Appendix
as a reference point for designing
your own diagrams.
4-2: Power Connections
The display units each include 2 isolated power input connections. This allows redundant
power sources, such as a main and secondary bus. The display units consume
approximately 1 amp, making even a 2 Amp-hour gel cell a suitable backup power source.
No provision is included within the display units for a power switch. If a power switch is
desired for the EFIS, the +12V power should be controlled with the switch, not the ground.
The display units include internal thermally-activated fuses. This protects the equipment
from internal electrical faults. Power supplied to the EFIS must pass through a fuse or
circuit breaker. It should be sized to allow at least 1.5 amps per display unit, with a
maximum rating of 5 amps.
Voltage drop in the power and ground wires will cause the EFIS voltmeter to read lower
than actual, by the amount of the voltage drop. For this reason, we recommend limiting
the length of these wires to 5 feet each, which will limit the voltmeter error due to this
effect to 0.15V.
The display unit monitors all power inputs; alarms are available to annunciate the loss of
any power source that was provided and is expected to be working according to the
“General Setup” menu.
The majority of the current flow into the display unit will occur on the bus with the highest
voltage.
If all the buses that power the display unit(s) and AHRS are also used to supply power to
the engine starter, then the display unit(s) and AHRS should be turned off during engine
start-up. This maximizes the current available for the starter and prevents undesirable
voltage fluctuations being applied to the display unit when it is booting up.
4-3: Ground Connections
The cable assembly provided includes 22 gauge wire for the ground return of the
display units. This will result in a voltage drop of about 0.015V/ft, which is acceptable for
wire lengths of up to five feet.
