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4.5 Dynamic Calibration Adjustment Procedure using the ECP-100

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

This procedure will allow adjustment to the calibration curve of the SSD120-(XX)N-RS5 or

SSD120-(XX)NE-RS5 using the ECP-100 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,

NOT

at the parallel data’s nominal transition point. See

Figure 1.

The

digitizer will 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.)

1. Connect the digitizer, ECP-100, NIST standard or flight altimeter as shown in the

Figure 2

and apply power.

2. Slide

the

ECP-100 CAL. PROGRAM

selector to the leftmost

PROGRAM

position.

3. Apply power to the altitude digitizer and slide the

ECP-100

power switch to the on position.

4. Set the altimeter barometric input to 29.92In.Hg. (1013MB). Adjust the static system

pressure and stabilize at the first altitude to be calibrated. The first possible correction for
Trans-Cal digitizers is at 0 feet. All adjustments to the digitizer calibration curve occur at
1000-foot intervals. Use the

ALTITUDE UP

and

ALTITUDE DOWN

buttons to adjust the

ECP-100

to the current pressure altitude prior to pushing the

INITIATE PROGRAM

pushbutton.

5. Press

the

INITIATE PROGRAM

pushbutton once. THE

ECP-100

will enter a digital

correction into the digitizer’s

EEPROM

at the current pressure altitude.

6. Adjust the input pressure to the next 1000-foot increment and adjust the

ECP-100

to the

next 1000-foot increment and repeat step 5. Continue repeating throughout the operating
range of the altitude digitizer.

7. Exercise the aircraft’s static system over the operating range of the altitude digitizer and,

with increasing and decreasing pressure, verify at a minimum of ten test points that the
altitude digitizer and primary flight altimeter correspond within the ±125 foot tolerance.
Lightly tap the altimeter before each reading to eliminate friction. If correspondence is not
achieved at any test point, the altimeter may require calibration.

8. Verify that the digitizer’s output is disabled when the transponder is not in mode “C”, or

when the “Altitude Disable” switch is in the off position.

NOTE:

If an error is entered into the digitizer, adjust the pressure to the correct altitude and re-enter the correction. To

clear

ALL

the corrections to the digitizer error curve press the

ALTITUDE UP PROGRAM

pushbutton once. Then

press and hold the

ALTITUDE DOWN

button for two seconds.

If the digitizer and flight altimeter are within the ±125-foot requirement then no correction is required.

DO NOT adjust the digitizer high and low potentiometers during or after this procedure.