Scientific Instruments

Measuring Instruments

Instrument	Measures / use	Key fact
Metre scale	Length	Least count commonly 1 mm (0.1 cm).
Vernier calipers	External/internal diameter, depth	More precise than a metre scale; least count depends on its design.
Screw gauge / micrometer	Very small diameter or thickness	Uses screw motion; least count = pitch ÷ number of circular-scale divisions.
Spherometer	Curvature/radius of spherical surfaces; small thickness	Uses a precision screw and three legs.
Measuring tape	Length or distance	Used for larger lengths; accuracy depends on scale and technique.
Stopwatch	Time interval	Digital models may measure small fractions of a second.
Balance	Mass	A beam balance compares masses; an electronic balance senses force and is calibrated to display mass.
Spring balance	Force / weight	Works using extension of a spring; reading depends on local gravitational acceleration.
Dynamometer	Force or torque, depending on type	A general name for force-measuring devices.
Sextant	Angle between two visible objects; traditionally celestial altitude	Historically used in navigation to determine position with other data.
Odometer	Distance travelled by a vehicle	Usually records wheel-related travel.
Speedometer	Instantaneous speed of a vehicle	Does not directly measure distance.
Tachometer	Rotational speed (rpm)	Used for engines and rotating machinery.
Altimeter	Altitude / height above a reference level	A barometric altimeter infers altitude from air pressure.
Clinometer	Angle of elevation or slope	Used in surveying and field measurements.
Theodolite	Horizontal and vertical angles	Surveying instrument.
Total station	Angles and distances; coordinates calculated	Electronic surveying instrument combining angle and distance measurement.
Laser rangefinder	Distance	Uses laser light and timing/phase methods.

Atmospheric and Weather Instruments

Instrument	Measures / use	Remember
Barometer	Atmospheric pressure	Mercury and aneroid types; falling pressure can indicate unsettled weather, but not by itself guarantee it.
Manometer	Pressure of a gas or liquid relative to another pressure	A U-tube manometer commonly uses liquid-column height.
Thermometer	Temperature	Mercury/alcohol liquid-in-glass and electronic types.
Maximum–minimum thermometer	Daily maximum and minimum air temperature	Commonly associated with Six’s thermometer.
Hygrometer	Humidity	A psychrometer uses wet- and dry-bulb thermometers.
Rain gauge	Rainfall amount	Usually reports depth of rainfall, e.g. millimetres.
Anemometer	Wind speed	A wind vane, by contrast, indicates wind direction.
Wind vane	Wind direction	Points to the direction from which wind blows.
Ceilometer	Cloud-base height	Used at airports and weather stations.
Pyranometer	Incoming solar radiation over a broad wavelength range	Commonly measures global solar irradiance on a surface.
Pyrheliometer	Direct-beam solar radiation	Usually aligned toward the Sun.
Sunshine recorder	Duration of bright sunshine	Campbell–Stokes is a traditional type.

Electricity, Magnetism and Electronics

Instrument	Measures / use	Key distinction
Ammeter	Electric current	Connected in series; ideal resistance is very low.
Voltmeter	Potential difference	Connected in parallel; ideal resistance is very high.
Galvanometer	Small electric current and its direction	Can be adapted into an ammeter or voltmeter with suitable resistors.
Ohmmeter	Electrical resistance	Circuit/component is normally measured with power off.
Multimeter	Voltage, current, resistance and other functions	A single instrument with selectable measurement modes.
Wattmeter	Electrical power	Measures power in an electrical circuit.
Energy meter	Electrical energy consumed	Household meters commonly record kWh.
Potentiometer	Potential difference / EMF by comparison	Null method can measure EMF without drawing current from the source at balance.
Megger (insulation tester)	High insulation resistance	Used to test electrical insulation.
Oscilloscope	Voltage signal versus time	Displays waveform; can help measure period, amplitude and frequency.
Frequency counter	Frequency of a periodic signal	Displays cycles per second, usually in hertz.
Transformer	Changes AC voltage/current level	Not a measuring instrument; common exam distinction.
Compass	Direction of magnetic north / local magnetic field direction	A simple magnetic compass aligns with the local field.
Fluxmeter	Magnetic flux change/flux, depending on design	Used in magnetic measurements.

Light and Optical Instruments

Instrument	Use	Key fact
Simple microscope / magnifying glass	Magnifies small objects	A convex lens.
Compound microscope	Views very small objects	Objective and eyepiece lenses.
Telescope	Views distant objects	Refracting telescopes use lenses; reflecting telescopes use mirrors.
Periscope	Views over or around obstacles	Traditional type uses mirrors or prisms.
Binoculars	Binocular viewing of distant objects	Two telescopes in one instrument.
Spectrometer / spectroscope	Studies spectrum; measures wavelengths or spectral features depending on type	Used in optical and chemical analysis.
Spectrophotometer	Measures light absorbance/transmittance at selected wavelengths	Used in chemistry and biology.
Photometer	Measures light intensity or related photometric quantities	Exact quantity depends on instrument type.
Lux meter	Illuminance	Unit: lux (lx).
Light meter	Measures light level for photography or other applications	May report illuminance or exposure-related values.
Polarimeter	Optical rotation of polarised light	Used to study optically active substances.
Interferometer	Uses interference to measure tiny changes in distance, wavelength or refractive index	High precision.
Optical pyrometer	High temperature without direct contact	Infers temperature from thermal radiation.

Heat, Sound and Laboratory Instruments

Instrument	Measures / use	Key fact
Calorimeter	Heat exchanged / specific heat or latent heat experiments	Ideally minimises heat exchange with surroundings.
Thermocouple	Temperature	Uses voltage generated at junctions of different conductors.
Pyrometer	High temperature	May be optical or radiation-based; non-contact types measure thermal radiation.
Hydrometer	Relative density / specific gravity of liquids	Floats at a level determined by liquid density.
Lactometer	Approximate density of milk	Does not alone prove milk purity or detect all adulteration.
Barograph	Continuous record of atmospheric pressure	A recording barometer.
Seismometer / seismograph	Ground motion from earthquakes	Seismometer is the sensor; seismograph traditionally refers to recording system.
Richter scale	Historically, earthquake magnitude	A scale, not an instrument; modern reporting often uses moment magnitude (Mw).
Sound level meter	Sound pressure level in decibels	Weighting networks such as dB(A) are commonly used.
Audiometer	Hearing sensitivity	Used in hearing assessment.
Stethoscope	Transmits body sounds for listening	Not a quantitative measuring instrument by itself.
Spirometer	Air volume and airflow during breathing	Used in pulmonary function testing.
Electrocardiograph (ECG/EKG)	Records electrical activity of the heart	Produces an electrocardiogram.
Electroencephalograph (EEG)	Records electrical activity of the brain	Produces an electroencephalogram.
Sphygmomanometer	Blood pressure	Manual or digital; often used with a stethoscope in manual measurement.

Space, Navigation and Earth Observation

Instrument / device	Use
GPS receiver	Estimates location, speed and time from satellite signals.
Radar	Detects objects and estimates range/speed using radio waves.
Sonar	Uses sound in water to detect objects or measure depth.
Echo sounder	Measures water depth from sound-echo travel time.
Lidar	Uses laser pulses to measure distance and map surfaces/atmosphere.
Seismograph	Records seismic waves; helps study earthquakes and Earth’s interior.
Magnetometer	Measures magnetic field strength or direction.
Gravimeter	Measures local gravitational acceleration or variations in gravity.
Radiometer	Measures radiant energy; exact use depends on type.
Dosimeter	Measures accumulated exposure to ionising radiation.
Geiger–Müller counter	Detects ionising radiation; counts detected events.
Cloud chamber	Makes tracks of charged particles visible through condensation.