An altimeter is an instrument that measures the altitude of any land surface or object such as an airplane. There are different kinds of altimeters such as pressure altimeters, aneroid barometer that approximately measures the altitude above the sea level by measuring atmospheric pressure, and radio altimeter that measures the absolute altitude based on the time required for a radio wave signal to travel from an airplane.
On What Principle does the Altimeter Work on?
The pressure altimeter works on the principle that average atmospheric pressure decreases linearly with altitude. A typical pressure altimeter is an instrument that is enclosed in a case connected to the outside of the aircraft by an air pressure inlet at the rear of the housing. Then, two or more aneroid capsules are positioned near the inlet. These are nothing but thin corrugated metallic bellows from which air has been exhausted. These capsules expand as soon as the outside air pressure falls and contracts when the outside air pressure rises. This is a mechanical arrangement of sector gears, crankshaft, pinion, backlash spring and the expansion and contraction of the aneroid capsules. All these are converted to the movement of pointers on the dial.
The graduated scale dial is marked off in meters or feet and then a series a gear-driven pointers similar to the hands of the clock can also be used to indicate the altitude in units of hundreds , tens or thousands. The barometric scale dial record the air pressure in millibars. Just because the atmospheric pressure is measured relative the sea level, a pressure altimeter is adjusted with the barosetting knob to compensate for smaller variations in the pressure caused by changes in the local weather.
Next, the radio altimeter also measures the distance of an aircraft from above the ground rather than the sea level. The altitude equates to one-half the time it takes a pulse of radio energy to travel from the aircraft to the ground and then back. This multiplied by the speed of the pulse. The measured altitude is the displayed on the video screen. Radio altimeters are used in automatic navigation and in blind-landing systems as well.
Best Altimeter Skydiving Gears
- Altimaster Galaxy Altimeter by Alti-2
This altimeter has user-replaceable lens. It also comes with a glow face in feet. It has large, bold numbers that are easy to read. The altimeter also has an engraved serial number. It has a robust machined aluminum casing that is available in many colors. It also has a sturdy hand mount.
- ARES II Digital Altimeter
This digital altimeter has an easy and fast altitude offset. It also comes with a quick back light with on an off feature. The altimeter has an anodized aircraft grade aluminum case. There is a large hi-def LCD screen. There is a scratchproof 2 mm thick hardened glass lens as well. This altimeter can store up to 10 minutes of profile data for your last jump.
These both are equally good altimeter skydiving gears depending upon your preference for digital or analog ones.