Ssd120-(Xx)M Calibration Adjustment Procedure - Trans-Cal SSD120 M Series Installation And Calibration Manual

4.5 SSD120-(XX)M Calibration Adjustment Procedure

This procedure is used to match the encoder/digitizer output to the flight
altimeter.
1. Construct a wiring harness per the Wiring Harness Diagram 881668 .
(This harness may be ordered directly from Trans-Cal Industries. Part
Number 881668 please specify 9 pin or 25 pin PC connector.)
2. Connect the digitizer, computer and altimeter as shown in the
Calibration Block Diagram 881669 , and energize. Set the altimeter
barometric reference to 29.92In.Hg. 1013.25MB.
3. Open the Hyper Terminal program as described in § 4.3 .
4. The digitizer output should now be displayed on the PC screen with 10
footresolution.
(You may use the Hyper Terminal "Clear Screen" function to remove
any extra characters that may be cluttering the screen. Click on Edit then
click on Clear Screen .)
Note: Backspace does not function in Hyper Terminal . If a typing error
occurs, hit <enter> and begin again.
5. Change the input pressure to -1000 feet and begin to compare the
altitude digitizeroutput, 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. ( § 4.7 provides a table to give the technician a
record of changes required and implemented.)
(Note: no digitizer correction is possible at the -1000 foot mark.)
The following procedure allows changes to the error curve of the digitizer.
6. Connect the encoder/digitizer as shown in the Calibration Block
Diagram 881669.
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