Page 5-26 400W Series Installation ManualRev. G 190-00356-025.4.4 ADC, Altitude Encoder, Fuel Sensor and Fuel/Air Data ComputerNOTEThis check does not apply to parallel connections to an altitude encoder. If the gray codeinterface to an altitude encoder is used, the check in Section 5.4.5 must be completed.The GNS 400W Series unit can receive altitude or fuel/air data from an external source. This checkverifies that the GNS 400W Series unit is receiving data from these units. Ensure that the GNS 400WSeries unit is turned on and in configuration mode. If the following steps do not perform correctly, checkthe 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 powerfrom all but one altitude source.3. Verify that pressure altitude (P ALT) data is being displayed and agrees with the active altitudesource.NOTEAfter 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 bedashed out.4. If there are multiple altitude sources, remove power from the currently active source and applypower 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 Altitude Encoder (Gray Code Connection)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 notperform 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:Pitot-Static TestSet AltitudeTolerance(ft)400 ± 20800 ± 202000 ± 3010,000 ± 8016,000 ± 11030,800 ± 1803. Verify that decoded altitude data is being displayed is equal to the test set altitude, within thetolerance specified.
