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4.9 Dynamic Calibration Adjustment Procedure
Reference: FAR 91.217; FAA Advisory Circular 43-6B
FAR 91.423; FAR 43-Appendix E and F
FAA TSO-C88a, EASA ETSO-C88a, SAE AS8003
SSD120-(XX)NE-RS5 as an aide in matching the digitizer output to a primary flight altimeter or
NIST traceable pressure standard. This procedure differs significantly from the Span Adjust
Procedure described in §4.4. The Dynamic Calibration Procedure makes adjustments to the
altitude data stored in the digitizer's EEPROM. The technician may make adjustments to the
digitizer error curve in 1000 foot increments, over the entire operating range with the single
exception of the –1000 foot mark. The technician will make the adjustments at the 0 or whole
altitude mark,
automatically adjust the ICAO parallel altitude data to transition 50 feet prior to the 0 mark. (i.e. the
digitizer's ICAO parallel altitude code will transition from 900 to 1000 feet while the serial altitude
data is transmitting 950 feet.)
9. Construct a wiring harness per the wiring harness diagram 881404.
10. Connect the digitizer, computer and altimeter or NIST standard as shown in the Dynamic
11. Open the Hyper Terminal program as described in §4.5.
12. The digitizer output should now be displayed on the PC screen with 10-foot resolution.
13. (You may use the Hyper Terminal "Clear Screen" function to remove any extra
Note: Backspace does not function in Hyper Terminal. If a typing error occurs, hit Q and begin
again.
14. Set the altimeter barometric input to 29.92 In. Hg. Change the input pressure to -1000 feet
(Note: No digitizer correction is possible at the -1000 foot mark.)
15. Type <enter> the digitizer will respond with ?>(current altitude).
16. Type ADJ <enter> the digitizer will respond with A=.
CAUTION: Always refer to the altimeter and VSI manufacturer's data for maximum rate of climb or descent
and any special test conditions which must be complied with.
17. Adjust the input pressure until the altimeter or NIST standard is exactly reading a 1000-foot
Example:
The altimeter reads 10,000 and the digitizer reports 10,080. Type "S10 <enter>"
This procedure will allow adjustment to the calibration curve of the SSD120-(XX)N-RS5 or
at the parallel data's nominal transition point. See Figure 1. The digitizer will
NOT
Calibration Block Diagram, and energize.
characters that may be cluttering the screen. Click on Edit then click on Clear Screen.)
and begin to compare the altitude digitizer output, as displayed on the computer, to the
altimeter reading at every 1000-foot mark. When the digitizer output begins to differ from
the altimeter by more than ±30 feet begin to change the digitizer error curve. (§4.9 provides
a table to for the technician to record the changes required and implemented.)
mark. Note the difference between the digitizer and the altimeter and adjust as follows.
Page 23 of 57
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