8. Master Reference Table — All Instruments
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The following consolidated table lists every instrument covered in this chapter for rapid, last-minute revision before the exam.
Instrument | What It Measures | Principle / Inventor |
Vernier Callipers | Small lengths, diameters, depth | Vernier scale; Pierre Vernier |
Screw Gauge | Very small thickness/diameter | Screw thread (pitch/least count) |
Odometer | Distance travelled by a vehicle | Wheel rotation counting |
Altimeter | Altitude above sea level | Atmospheric pressure change (aneroid barometer) |
Fathometer | Depth of water bodies | Echo-ranging (ultrasonic sound) |
Sonar | Underwater distance/detection | Sound wave echo |
Barometer | Atmospheric pressure | Mercury column; Evangelista Torricelli |
Thermometer | Temperature | Thermal expansion of liquid |
Pyrometer | Very high temperature | Radiation intensity (non-contact) |
Hygrometer | Humidity | Wet-bulb/dry-bulb comparison |
Anemometer | Wind speed | Rotating cups; John T. R. Robinson |
Speedometer | Vehicle speed | Magnetic eddy current / electronic sensor |
Tachometer | Rotational speed (RPM) | Rotation counting per unit time |
Spring Balance | Weight/force | Hooke's Law |
Hydrometer | Relative density of liquids | Flotation (Archimedes' principle) |
Manometer | Pressure of enclosed gas/fluid | Liquid column height difference (U-tube) |
Viscometer | Viscosity of fluids | Flow rate/drag measurement |
Seismograph | Earthquake intensity/duration | Inertia of suspended mass |
Calorimeter | Quantity of heat | Conservation of energy |
Dynamometer | Force, torque, engine power | Measured resisting load on a shaft |
Chronometer | Precise time (marine navigation) | High-precision mechanism; John Harrison |
Rain Gauge | Amount of rainfall | Funnel + calibrated cylinder |
Bolometer | Intensity of radiant heat | Resistance change of heated strip; Samuel P. Langley |
Barograph | Atmospheric pressure over time | Self-recording aneroid barometer |
Ammeter | Electric current | Moving-coil deflection; series connection |
Voltmeter | Potential difference (voltage) | High resistance; parallel connection |
Galvanometer | Presence/direction of small current | Torque on coil in magnetic field |
Ohmmeter | Electrical resistance | Ohm's Law (applied voltage/measured current) |
Wattmeter | Electric power | Current coil + voltage coil product |
Multimeter | Voltage, current, resistance | Combined selectable circuit |
Potentiometer | EMF/potential difference (comparative) | Null-deflection balance point |
Simple Microscope | Magnifies small objects | Single convex lens |
Compound Microscope | High magnification of minute objects | Objective + eyepiece lens system |
Telescope | Views distant objects | Objective lens (Galileo) / concave mirror (Newton) |
Periscope | Views objects out of line of sight | Two parallel mirrors/prisms at 45° |
Binoculars | Stereoscopic distant viewing | Twin telescopes with prisms |
Spectrometer | Light spectrum/composition analysis | Dispersion via prism/grating |
Photometer | Light intensity | Illumination comparison / photoelectric sensing |
Refractometer | Refractive index/concentration of a solution | Critical angle for total internal reflection |
Audiometer | Hearing acuity | Calibrated pure tones |
Sonometer | String vibration frequency | Resonance box with stretched wire |
Stethoscope | Heart/lung sounds | Air-column sound transmission; René Laennec |
Megaphone | Amplifies/directs sound | Directional sound projection |
Sphygmomanometer | Blood pressure | Inflatable cuff + manometer/oscillometric sensor |
Endoscope | Interior of body cavities/organs | Fibre-optic camera tube |
ECG / EKG | Electrical activity of the heart | Skin electrodes; Willem Einthoven |
Ophthalmoscope | Interior of the eye | Mirrors/prisms with illumination |
Otoscope | Ear canal and eardrum | Light + magnifying lens on speculum |
Electroencephalograph (EEG) | Electrical activity of the brain | Scalp electrodes; neuronal signals |
Phonocardiograph | Heart sounds/murmurs (graphical record) | Microphone-based recording |
Compass | Geographical direction | Magnetised needle aligns to Earth's field |
Sextant | Angle of elevation of celestial body | Two mirrors on graduated arc |
Gyroscope | Orientation/angular velocity | Conservation of angular momentum |
Radar | Distance/speed of objects (radio waves) | Radio wave echo/reflection |
Lidar | Precise distance/3-D mapping (laser) | Laser light echo/reflection |