Question

Which instrument is used to measure altitudes in aircrafts?

Answer 1

Altimeters are used for the measurement of height during takeoff and landing operation for the clearance of the terrain obstacles during a route of operation and for the vertical separation of aircraft’. Aircraft is a vehicle that is able to fly by the support of air; it counters the force of gravity by using static lift or dynamic lift of an airfoil.

Complete step-by-step solution:
Altimeter is used to measure altitudes in aircrafts.The altimeter is pressure operated instrument .it is similar to barometer expect that it uses units of distance(meters or feet).it works by measuring air pressure and also utilizing the fact the air pressure of the atmosphere decreases by approximately 1millibar for each 10meters in height .
The pressure measured is static pressure which is dependent on airspeed of the aeroplane. The principle of operation is that a compressible, sealed metal canister contains a fixed amount of air .When the external air pressure reduces (as the aeroplane’s altitude increases) the canister expands .this movement is transmitted via a mechanical linkage to an instrument dial. The dial normally has two pointers with units of ${{10}^{3}}$ and ${{10}^{2}}$ meters (or feet) to make it easy to read quickly.
For normal aviation the altimeter is zeroed using the international standard atmosphere (ISA) which assumes a mean sea level pressure of 1013.2 millibars . The altimeter is calibrated to read zero altitude at this external pressure and aircraft height height above this level is formally known as pressure altitude .as a pressure operated instrument, the altimeter is sensitive to any errors in the ‘static pressure sensing point and to mechanical inertia delays in the aneroid bellows
The mechanism of the altimeters used in service operations are either mechanical or electrical (served systems or pressure- transducer systems).with the electrical systems, corrections for the position errors of the static-pressure installation are applied automatically so that the displayed altitude is the correct value.
A mechanical type altimeter has two scales

An altitude scale with the altitude displayed by a rotating pointer and a revolving drum.
A barometer scale with the atmospheric pressure displaced on adjustable drum
The mechanism that rotates the pointer drum displayed and the barometric sub-dial interconnected so that an adjustment of sub dial gives for a given pressure increment produces a rotation of the altitude display to a corresponding increment in altitude. With the altitude display,
The pointer rotates one revolution per 1000ft, while the two digit drum rotates to indicate 1000-ft and 10,000-ft increments.
Additional information:
Ammeter: measure the current
Audiometer: measures intensity of sound
Anemometer: measures direction force and velocity of wind

Note: Students' altitude is determined based on the measurement of atmospheric pressure. Greater the altitude lower will be the pressure and altimeters are similar or alike of barometer. Barometer with a nonlinear calibration which is used to indicate the altitude is called a pressure altimeter or barometric altimeter.