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Section 4.0 Calibration and Configuration
4.1 Calibration Overview:
SSD120-(XX)A-RS or SSD120-(XX)AE-RS as an aide in matching the digitizer
output to a primary flight altimeter or NIST traceable pressure standard. The
maximum allowed error between the primary flight altimeter and the altitude
digitizer is "125 feet as required by TSO-C88a. All Trans-Cal digitizers are
calibrated to NIST traceable pressure standards; however, the error allowed on
altimeters at higher altitudes can lead to a combined error in excess of "125 feet.
device. The technician need only perform the method which is best suited for the
application in question. There is no need to perform both methods. The digitizer
may be adjusted using the two potentiometers which are the traditional method of
adjusting the span and reference of a solid state digitizer. This device may also be
adjusted utilizing an externally addressable EEPROM which is configured to
accept an alternate error curve entered to the digitizer via an IBM compatible PC.
where the only a slight modification is required to bring the altitude digitizer
curve up or down.
match the altitude digitizer to the primary flight altimeter. It assumes the digitizer
and altimeter are connected through the static line and the technician may adjust
the input pressure to run the digitizer and primary flight altimeter to the same
altitude and then enter this altitude into an IBM compatible computer which will
transmit the correction to the digitizer=s EEPROM.
4.2 Required Equipment Span Adjust:
(See span adjust block diagram.)
1. Primary Flight Altimeter.
2. +12 to 28VDC power supply.
3. A pitot-static test set, capable of exercising the altimeter and digitizer over a
range of -1000 feet to the maximum altitude of the digitizer.
4. A ramp checker or test set capable of interrogating the transponder.(Optional:
ATS-200 or equal device which will allow the display of the 100 foot
resolution parallel altitude data.)
This procedure will allow adjustment to the calibration curve of the
There are two different methods used to affect the calibration of this
The Span Adjust calibration ('4.4) is normally used in applications
The Dynamic Calibration procedure ('4.7) is another method used to
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