REVUE THOMMEN AG
CH-4437 Waldenburg
AD20 Standby Altimeter
Page 42 of 72
07-Sep-2009 Document No: AD-INSOP-800 Revision: 1.6
AD20 Standby Altimeter
(no Battery, no ARINC429)
Power Consumption
Operation Lighting on / maximum
(5 VDC)
Lighting off / minimum
(5 VDC)
Primary Power 28 VDC
During startup max. 4.0 W / 140 mA max. 3.4 W / 120 mA
Normal operation 1.7 W / 60 mA 1.4 W / 50 mA
Table 4-1 Power Consumption
NOTE: Power supply for the Lighting of LED (Liquid Crystal Display ) are supplied internally in the
instrument from primary or secondary power. Whereas this lighting supply input is only used to
control its intensity (SEE A.5 for details) according to the lighting voltage (input current draw form
lighting power supply is less than <15 mA).
4.1.4.4 Power Failure indication
In case of power supply failure or switching off the warning flag valid output discrete (WFVOUTD) will
be set to invalid (open = invalid condition, ground = valid operation).
4.1.4.5 Groundings and Shielding
Groundings
All the ground strap chassis grounds aircraft, twisted shielded cables/wires and power cables/wires
(SEE section B.2 wiring diagram for the grounding cables/wires) should be carefully grounded
(aircraft ground & shield grounds) such a manner in order to :
• prevent ground loops and common ground returns for signals and power circuits
• provide effective shielding for signal circuits
• minimize EMI (Electromagnetic Interference) during the engine run-up, and
• protect personnel from electrical shock hazards.
Note: All externally exposed metal parts, shields, connectors, etc. are grounded to the chassis
ground.
4.1.4.5.1 Harness with shielded power wires, RF Susceptibility Cat. [YY]
The GROUND strap should be electrically connected to the mating connector with conductive over-
braided shielding and the other end shall be connected to aircraft ground.
NOTE: The maximum length of the GROUND strap : 30 cm (12 inches)
To meet RTCA/DO-160D, RF Susceptibility, Section 20, Cat. [YY], all wires shall be shielded
according to 4.1.4.5.1 Harness with shielded power wires, RF Susceptibility Cat. [YY].
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