Garmin GI 275 Installation Manual page 91

8. RPM Sensor
Methods for RPM sensing appropriate to the engine should be selected as follows:
1. P-lead sensor – One per magneto or two per dual magneto. Resistors must be installed in
accordance with Figure B-8 and Figure B-10.
2. Magneto vent mounted sensor – Not compatible with geared engines. One sensor for each
engine on non-pressurized magnetos only (e.g., Bendix -20, -21, -200, 1200 series, and Slick
6000, 4000 series).
9. Shunt
Compatible shunts are listed in Appendix Section C.19. The EIS configuration setting must match the
shunt rating and type. The shunt rating is the maximum current and is typically marked on the shunt.
The type is the voltage between the shunt posts at maximum current rating. The shunt rating and type
may also be found in the aircraft data.
If the shunt rating cannot be determined by part markings or the aircraft data, the following procedure
may be used for 50 mV shunts:
1. With the aircraft power ON, no ground-power applied, and a minimal electrical load ON,
measure the millivolts between the shunt terminals using a calibrated voltmeter. Record the
millivolt measurement (V1).
2. Apply an electrical load (L1) as follows:
a. If an alternator load meter is installed, the shunt will measure the charging current from
the alternator to the main bus. With the engine running, apply an electrical load and
measure the current (L1) from the alternator using a calibrated ammeter. Measure and
record the new shunt millivolt value (V2).
b. If a battery ammeter is installed, the shunt will measure the current from the battery to the
main bus. Without the engine running, apply an electrical load and measure the current
(L1) from the battery using a calibrated ammeter. Measure and record the new shunt
millivolt value (V2).
3. Record the millivolt change (V
4. Determine the shunt rating using the following calculation
If the shunt value cannot be determined, retain the existing gauge(s) or install an appropriately rated
compatible 50 mV shunt. Shunt installation is outside the scope of this STC and must be approved
using other means.
10. Outside Air Temperature (OAT)
For standalone EIS installations that display horsepower but do not have an air data computer in the
system, an OAT probe can be connected to the GEA 24/110 as an EIS sensor. Refer to Appendix
Section C.19 for sensor compatibility.
190-02246-10
Rev. 11
) between steps 1 and 2. V
change
Shunt Rating (Amps) =
= V2 - V1.
change
.
L1 (Amps) x 50mV
V (mV)
change
GI 275 Part 23 AML STC Installation Manual
Page 3-28