MGL Avionics Stratomaster Ultra Horizon XL Owner’s manual
Page 62
CARING FOR THE STRATOMASTER ULTRA
Pitot tube
Dust etc. can cause a blockage in the pitot tube. Such blockage will effect the operation of
the pitot tube which will in turn affect the accuracy of the ASI/TAS readings. We recommend
that the pitot tube be covered when the aircraft is not in operation.
Cleaning
The Stratomaster Ultra can be cleaned by wiping it with a damp cloth. A mild soap may be
used if necessary.
Take care not to wet the instrument excessively.
Do not use chemicals e.g. petrol, spirits, turpentine when cleaning the instrument.
Never clean the non-reflective display lens with abrasive cleaners or cleaners containing
solvents as this will destroy the lens coating.
Calibration
The Stratomaster Ultra instrument does not require re-calibration if it is used in normal
operation.
Stratomaster Instruments used as references to calibrate other instruments may be sent in
for periodic calibration to MGL Avionics. For this application we recommend a two year
calibration interval. Please contact MGL Avionics for details.
Altimetry
This section is intended to clarify how an altimeter works and what determines its accuracy in
simple terms.
As you know an altimeter is a simple absolute pressure gauge. This means it measures the
pressure of the surrounding air relative to absolute vacuum as you would find in outer space.
Ordinary, well made altimeters are intricate mechanical devices that can achieve very good
performance. However, these are subject to a whole host of influences that introduce errors
in the readings. Vibrations tend to wear out the tiny gears, temperature has an effect on the
elasticity of the materials used and therefore has a direct influence on the reading. The
quality of the vacuum has a direct bearing on errors and the maximum altitude the instrument
can indicate with a reasonable error.
The Stratomaster Ultra is based on a silicon pressure sensor. In principle, these sensors are
subject to many of the problems that affect ordinary mechanical instruments and many digital
altimeters have poor accuracy and resolution.
What is different in the Stratomaster Ultra?
The Stratomaster Ultra employs the most accurate absolute pressure sensor available. This
sensor is not cheap or simple. It starts with a tiny cavity in a silicon chip. This cavity is about
¼ mm
3
in size and contains a near perfect vacuum. It is sealed with a very thin membrane
that is only a few thousand atoms thick. The air pressure on the one side of this membrane
bends the membrane towards the vacuum cavity. This introduces tiny changes in the
