Garmin GPS 400W Installation Manual page 106

5.4.4 A DC, Altitude Encoder, Fuel Sensor and Fuel/Air Data Computer
1 8 1 B
This check does not apply to parallel connections to an altitude encoder. If the gray code
interface to an altitude encoder is used, the check in Section
The GNS 400W Series unit can receive altitude or fuel/air data from an external source. This check
verifies that the GNS 400W Series unit is receiving data from these units. Ensure that the GNS 400W
Series unit is turned on and in configuration mode. If the following steps do not perform correctly, check
the electrical connections and configuration setup.
1. Go to the Main Inputs 1 page.
2. If there are multiple altitude sources providing data to the GNS 400W Series unit, remove power
from all but one altitude source.
3. Verify that pressure altitude (P ALT) data is being displayed and agrees with the active altitude
source.
After applying power to an altitude source it may take several minutes to warm up.
During the warm-up period the altitude display on the GNS 400W Series unit will be
dashed out.
4. If there are multiple altitude sources, remove power from the currently active source and apply
power to another source that has not been checked.
5. Repeat steps 3 and 4 until all available altitude sources have been checked.
5.4.5 A ltitude Encoder (Gray Code Connection)
1 8 2 B
The GNS 400W Series unit can receive altitude from an external gray code encoder or encoding altimeter.
This check verifies all of the connections in the parallel gray code interface. If the following steps do not
perform correctly, check the electrical connections and configuration setup.
1. Go to the Main Discrete Inputs page.
2. Using a pitot-static test set, set the altitude to the values specified below:
3. Verify that decoded altitude data is being displayed is equal to the test set altitude, within the
tolerance specified.
Page 5-26
Rev. F
NOTE
NOTE
Pitot-Static Test Tolerance
Set Altitude
400
800
2000
10,000
16,000
30,800
5 .4.5 must be completed.
4 4 7 H
(ft)
± 20
± 20
± 30
± 80
± 110
± 180
400W Series Installation Manual
190-00356-02