Physics Measuring Instruments

A manometer measures pressure of liquids and gases using fluid columns or electronic sensors. The Greek 'mano-' refers to pressure (related to 'thin' or 'rarefied'). Micrometers gauge tiny distances, algometers measure pain sensitivity, and tensimeters assess surface tension.

Radar is a device used for detecting distant objects.

Correct option is (3).

A hypsometer is an instrument used to measure altitude or height above sea level. It works by measuring the boiling point of water, which decreases with increasing altitude due to lower atmospheric pressure. Hygrometers measure humidity, voltmeters measure electrical potential difference, and amperemeters measure electric current.

DME measures the slant range (direct line distance) from the aircraft to the DME ground station, not the horizontal distance over the ground. As an aircraft flies directly overhead, the DME shows the aircraft's altitude at that point. True altitude and vertical guidance are provided by other instruments like altimeters and glidepath indicators.

GPS uses satellite triangulation and time-of-arrival calculations, not gyroscope principles. The Turn and Slip indicator and Heading Indicator both use gyroscopes - the former uses a rate gyro to detect turn rate, while the latter uses a directional gyro to maintain heading reference. Gyroscopic instruments rely on the principle of rigidity in space and precession.

A barometer is the scientific instrument specifically designed to measure atmospheric pressure. It works based on principles of fluid displacement (mercury barometers) or mechanical deformation (aneroid barometers). Thermometers measure temperature, ammeters measure electric current, and neither of these can measure air pressure.

 Increase in length of a plant can be measured by an instrument called auxanometer.

A sphygmomanometer is the medical instrument used to measure blood pressure. It typically consists of an inflatable cuff wrapped around the arm and a pressure gauge that displays systolic and diastolic readings. Options A, C, and D refer to other medical parameters (blood sugar, bone density, and white blood cell count) that require different diagnostic tools.

Basic training aircraft like the Cessna-152 are manually flown and do not have autopilot systems to keep costs low and teach fundamental flying skills. The other instruments listed (VSI, altimeter, airspeed indicator) are essential flight instruments present on all aircraft including trainers. Autopilot is found on more advanced or complex aircraft.

A voltameter is an instrument used to measure potential difference (voltage) between two points in an electrical circuit. It works on the principle of electromagnetic induction and provides readings in volts.

In aircraft instruments, the static port provides ambient atmospheric pressure readings. The altimeter uses ONLY static pressure to calculate altitude by comparing it to a reference pressure (standard atmosphere). The airspeed indicator requires both pitot pressure (ram air pressure) and static pressure to calculate airspeed. Machmeters need pitot, static, and temperature data.

The pitot-static system connects to the pitot tube (measuring ram air pressure) and static port (measuring ambient pressure). Instruments using this system include the altimeter, vertical speed indicator, and airspeed indicator. The alteter uses static pressure only. Directional gyro is gyroscopic, TSI is turbine-based, and GPS is satellite-based.

Pitot-static instruments are those that use pitot (dynamic) and static pressure measurements: ASI (Airspeed Indicator), VSI (Vertical Speed Indicator), and Machmeter all operate on pitot-static principles. VOR (VHF Omnidirectional Range) is a radio navigation system that operates on radio waves, not pressure. It is fundamentally different from pitot-static instruments.

A Machmeter reading depends on the aircraft's speed relative to the speed of sound at the local altitude. The speed of sound varies with temperature, which varies with altitude. Therefore, the Machmeter responds to changes in speed, altitude (through temperature), and temperature directly. Aircraft weight affects lift and stall speed but does not influence the Mach number calculation or display.