An altimeter or height meter is the instrument used to measure the altitude of an object over a fixed level. The altitude measurement is called altimetry , which corresponds to the bathymetry term, underwater depth measurement.
Video Altimeter
Altimeter tekanan
The altitude can be determined based on atmospheric pressure measurement. The higher the height, the lower the pressure. When the barometer is equipped with nonlinear calibration to indicate altitude, it is called a pressure altimeter or barometric altimeter. A pressure altimeter is the altimeter found in most planes, and skydivers use versions mounted on the wrist for similar purposes. Mountaineers and mountaineers use altimeters mounted on the wrist or handheld, in addition to other navigation tools such as maps, magnetic compasses, or GPS receivers.
Kalibrasi altimeter menikikuti persamaan
where c is a constant, T is the absolute temperature, P is the pressure at z height, and P o is the pressure at sea level. The c constant depends on the acceleration of gravity and the mass of the air molar. However, we must realize that this type of altimeter depends on "altitude" and its readings may vary by hundreds of feet due to sudden changes in air pressure, such as from a cold front, without altering the actual height.
Use in climbing, climbing and skiing
A barometric altimeter, used in conjunction with topographic maps, can help to verify a person's location. This is more reliable, and often more accurate, than a GPS receiver to measure altitude; GPS signals may not be available, for example, when someone is deep within a canyon, or may provide a very inaccurate height when all available satellites are near the horizon. Because barometric pressure changes with the weather, climbers should periodically re-calibrate their altimeter as they reach a known height, such as a crossroads or peaks marked on a topographic map.
Skydiving
An altimeter is the most important piece of skydiving equipment, after the parachute itself. Awareness of awareness is essential all the time during a jump, and determining the right response to maintain safety.
Since height awareness is essential in skydiving, there are a variety of altimeter designs made specifically for use in sports, and non-student skydivers will typically use two or more altimeters in a single jump:
- Analog visual altimeter hand, wrist or chest mechanic. This is the most basic and common type, and is used by (and generally mandated for) almost all skydivers students. The general design has a marked face from 0 to 4000m (or 0 to 12000 ft, mimicking the face of the clock), where the arrow points to the current height. The plank section of sport is marked prominently in yellow and red, indicating the recommended placement height, as well as the height of the decision of the emergency procedure (commonly known as the "hard deck"). A mechanical altimeter has a button that needs to be adjusted manually to make it point to 0 on the ground before jumping, and if the landing point is not at the same height as the takeoff point, the user needs to adjust it appropriately. Several sophisticated electronic altimeters are also available that use familiar analogue displays, though internally operate digitally.
- Digital visual altimeter , mounted on the wrist or hand. This type always operates electronically, and conveys altitude as a number, not a pointer on the dial. Since this altimeter already contains all the electronic circuits required for elevation calculations, they are generally equipped with additional functions such as electronic logbooks, real-time jumping profile replays, speed indications, simulator modes for use in ground training, etc. An electronic altimeter is activated on the ground before jumping, and it calibrates automatically to point to 0. It is thus important that the user does not turn it on earlier than necessary to avoid, for example, a drive to a dropzone located at different altitudes of one's home that may cause fatal wrong reading. If the landing zone is at an altitude different from the takeoff point, the user needs to enter the appropriate offset using the specified function.
- Audible altimeter (also known as "dytters", the generic trademark of the first product on the market). It is inserted into one's helmet, and emits a warning tone at a predetermined height. Contemporary audible has evolved significantly from their rough start, and sports a wide range of functions, such as multiple tones at different heights, multiple stored profiles that can be switched quickly, electronic logbooks with data transfer to PC for later analysis, free fall freely and canopy modes with different warning heights, the tone of the approaching approach, etc. Audibles are a very strict tool, and do not replace, but complement the visual altimeter that remains the primary tool for maintaining altitude awareness. The advent of modern skydiving disciplines such as freeflying, where the land may not be in someone's field of view for long periods of time, has made the use of audibles almost universal, and almost all skydiving helmets come with one or more built-in ports where sounds may be placed. Audibles are not recommended and are often prohibited from use by skydivers students, who need to build a proper height awareness regime for themselves.
- Additional visual altimeters . It does not show the right height, but it helps to maintain a common indicator in a person's peripheral vision. They may operate in conjunction with sounds equipped with appropriate ports, in which case they emit flashing warnings that complement audible, or stand-alone tones and use other display modes, such as showing green or red light depending on the height./li>
The exact choice of altimeter depends heavily on individual jumpers' preferences, level of experience, major discipline, and leap type. At one end of the spectrum, a low altitude demonstration jumps with a water landing and there is no free fall which may rule out the use of a mandatory altimeter and not use it at all. In contrast, jumpers jumper jumping and flying with high performance canopies may use mechanical analog altimeters for easy reference in free fall, an audible in-helmet for altitude breaking alerts, as well as programmable tones for flying canopy, as well as altimeter digital captain on the armband to quickly glance at the exact height of the approach. Other skydivers who perform similar types of jumps may be using digital altimeters for their primary visuals, preferring a height reading directly from the numerical display.
Use in airplane
Inside the plane, the aneroid barometer measures atmospheric pressure from a static port outside the plane. Air pressure decreases with elevation - about 100 hectares per 800 meters or one inch of mercury per 1000 feet near sea level.
The aneroid altimeter is calibrated to show the direct pressure as altitude above the mean sea level, in accordance with the atmosphere of the mathematical model determined by the International Standard Atmosphere (ISA). The older aircraft used a simple aneroid barometer where the needle made less than a revolution around the face from scratch to full scale. This design evolved into an altimeter with a primary needle and one or more secondary needles showing the number of turns, similar to a face clock. In other words, each needle points to a different digit than the current altitude measurement. However this design is not preferred because of the risk of misreading in stressful situations. The design evolved further into the drum-type altimeter, the final step in analog instrumentation, where every single needle revolution accounted for 1,000 feet, with a thousandfold increment recorded on the odometer-type numerical drum. To determine the altitude, a pilot must first read the drum to determine thousands of feet, then see the needle for hundreds of feet. Modern analog altimeter in a transport plane is usually a drum type. The latest development in clarity is an electronic flight instrument system with integrated digital altimeter display. This technology has trickled from military planes and aircraft to standard today in many common aviation aircraft.
Modern aircraft use "sensitive altimeter". At a sensitive altimeter, the surface reference reference pressure can be adjusted with the adjustment button. Reference pressures, in inches of mercury in Canada and the United States, and hectopascal (elsewhere milibs) elsewhere, are displayed in a small Kollsman window in front of the aircraft altimeter. This is necessary, since atmospheric reference atmospheric pressure at a particular location varies over time with the temperature and movement of the atmospheric pressure system.
In flight terminology, regional or local air pressure at the mean sea level (MSL) is called QNH or "altimeter setting", and the pressure that will calibrate the altimeter to indicate the above ground level in a given airfield is called QFE from the field. However, the altimeter can not be adjusted for air temperature variations. The temperature difference of the ISA model will cause errors in the indicated height.
In space, a stand-alone mechanical altimeter based on a diaphragm bellows is replaced by an integrated measurement system called an air data computer (ADC). This module measures altitude, flight speed and outside temperature to provide more accurate output data allowing automatic flight control and flight level divisions. Some altimeters can be used to design pressure reference systems to provide information about the angle of the plane position to support further inertial navigation system calculations.
Maps Altimeter
Use in ground effect vehicle
After extensive research and experiments, it has been shown that "radio-altimeter phases" are best suited for vehicles with soil effects, compared with laser, isotropic or ultrasonic altimeter.
Sonic altimeter
In 1931, the US Army Air Corps and General Electric tested the sonic altimeter for aircraft, which were considered more reliable and accurate than those that relied on air pressure when thick fog or rain was present. The new altimeter uses a series of high-pitched sounds as made by bats to measure the distance from the plane to the surface, which returns to the plane being transformed into the foot indicated on the gauge inside the aircraft cockpit.
Radar altimeter
The radar altimeter measures the altitude more directly, using the time taken for the radio signal to reflect from the surface back to the plane. Alternatively, Frequency Modulation, continuous wave radar can be used. The larger the frequency shifts the further distance traveled. This method can achieve much better accuracy than the pulsed radar for the same expenditure and the radar altimeter that uses frequency modulation is the industry standard. Radar altimeter is used to measure altitude above ground level when landing on commercial and military aircraft. The altimeter radar is also a component of the field avoiding warning system, alerting the pilot if the aircraft is too low, or if there is a rising field ahead. The altimeter radar technology is also used in radar that follows a field that allows the fighter to fly at very low altitudes.
Global Positioning System
The Global Positioning System (GPS) receiver can also determine altitude with trilateration with four or more satellites. In an aircraft, the altitude determined using an autonomous GPS is not sufficiently reliable to replace the pressure altimeter without using some augmentation methods. In climbing and climbing, it is not uncommon to find that the height measured by GPS is turned off by 400 feet depending on the satellite orientation.
Other transport modes
The altimeter is an optional instrument in off-road vehicles to aid navigation. Some high-performance luxury cars never intended to leave paved roads, such as the Duesenberg in the 1930s, are also equipped with an altimeter.
Climbers and mountain climbers use hand-held or wrist-installed barometric alometymeters, just like skydivers.
Diesel subss have a barometer mounted on them to monitor the vacuum drawn in the event that the snorkel closes while the diesel engine is running and, as a result, sucks air from the boat.
See also
- Acronyms and abbreviations in avionics
- Flight instrument
- Flight rate
- Hypsometer
- Jason-1, Marine Topographic Mission/Jason-2 is the current satellite mission that uses altimeters to measure sea level
- Altimeter laser
- Radar altimeter
- Level sensors
- Sensor pressure
- Variometers, gauges that measure altitude changes
- Turkish Airlines Flight 1951, an accident associated with a non-working radio altimeter
- United Airlines Flight 389, accident due to misreading altimeter
- Satellite altimetry
References
External links
Source of the article : Wikipedia
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