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1. Altimeter:

It is also known as altitude meter. It is used to measure the

altitude or distance of an object above a fixed level such as the

earth' surface, water surface, etc.

For example, it can measure the altitude of an airplane,

spacecraft, etc., from the earth or sea surface.

2. Ammeter:

This scientific instrument is used to measure the electric

current. The electric current is a flow of electrons that is

measured in ampere. So, it is the instrument that measures

the current in ampere, so it is called an ammeter or ampere

meter.

3. Anemometer:

It is used to measure the speed, direction and pressure of wind

in the atmosphere, in wind tunnels, houses, and more.

It is provided with a spinning wheel. The stronger the wind

blows, the faster the wheel rotates.

4) Audiometer

It is designed to measure the intensity of sound while

evaluating hearing acuity. It is widely used by audiologists and

other trained medical practitioners to check the hearing

threshold of a person and to identify and quantify the degree of

hearing loss in a person. From the findings and readings

obtained using this device, appropriate medical treatment and

hearing aid fitting can be prescribed. These instruments are

commonly found in ENT (ear, nose, and throat) clinics and

other audiology centres.

5) Barometer

It measures the atmospheric pressure, the pressure exerted by the air

on the Earth's surface. Our atmosphere comprises different layers of

air wrapped around the Earth. Due to gravitational pull towards

Earth, the air presses against everything it touches, this pressure of

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air is called atmospheric pressure and is measured by a barometer. Atmospheric

pressure changes with distance above or below sea level.

6) Electron microscope

It is used to see extremely small objects such as atoms, bacteria or

viruses. Its magnification or resolving power is very high as

compared to ordinary microscopes.

The electron microscopes can magnify an object up to two million

times as compared to a light microscope which can magnify only

up to 2000 times. The first electron microscope was invented in

1931 by German engineers Max Knoll and Ernst Ruska.

7) Endoscope

This instrument is used to examine or view the internal organs

inside our body without performing surgery.

It is used to examine organs such as throat, oesophagus,

stomach, etc. It can be inserted into the body through mouth,

anus or through a small cut made in the skin during keyhole

surgery. Besides this, an endoscope is also used to take a biopsy

(removal of tissue) to examine a disease.

8) Fathometer:

It is a scientific instrument that is used to measure the depth of

water, e.g. ocean depth. It is mostly used by ships to find out

the depth of water below the ships. Fathometer is an echo-

sounding instrument that uses sound waves to calculate the

depth of water. The first practical fathometer was invented by

Herbert Grove Dorsey, an American engineer. It was more

precise and easier to use than other instruments based on sounding methods. So, it

became an important tool for the survey of oceans.

9) Galvanometer

It is used to detect or measure the presence of small electric current

and voltage. It also detects the direction of the current flowing in the

circuit and the null point of the circuit.

The first galvanometer was invented by Johann Schweigger in 1820.

The movement of the coil in a magnetic field indicates the presence of

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the current and its intensity. So, its main function is to detect the presence, direction of

flow and the intensity of current in a conductor.

10) Hydrometer

It is a scientific instrument that is designed to measure the relative

density or specific gravity of different types of liquids. This instrument

works on the Archimedes' principle which says that the buoyant force

exerted by the water on a submerged object is equal to the weight of the

water displaced by the submerged portion of the object. They are mostly

used by winemakers to test the sugar content of wine and by the scientists for soil

analysis.

11) Hydrophone

This scientific instrument is an underwater device designed to

detect, monitor and record underwater sounds coming from

different directions. Just like a microphone receives sounds in

the air, it receives acoustic signals in the water.

These days, the hydrophones are mostly used for listening to

the sounds of underwater life and natural phenomena such as

waves, earthquakes, and underwater volcanic eruptions.

Besides this, it can also be used for underwater mapping, underwater communication

and navigation.

12) Hygrometer

It is used as a weather instrument as it is designed to measure the

humidity in the air or atmosphere. Humidity is the amount of

water vapour present in the atmosphere. The uncomfortable

sticky feeling in summers is due to the high humidity in the air.

The most commonly used hygrometer is called a psychrometer.

Horace Benedict de Saussure had designed one of the first

hydrometers in 1783. This type of hygrometers is suitable for measuring humidity in the

outdoor areas and indoor places such as storage areas where dry conditions need to be

maintained.

13) Hypsometer

It is used to measure the height or elevation of an object such as a

building, tree, etc. A hypsometer can be of different types based

on the principles it uses to measure the height. It is most often

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used for survey and by the construction industries to measure the height of buildings

and by arborists to measure the heights of trees.

14) Machmeter

It is a scientific instrument that measures the ratio of the speed of

the aircraft to the speed of the sound, this ratio is called Mach

Number (M). This instrument is very important for the aircraft that

fly at high speed. The pilot can easily understand whether he is

flying within the safe speed limits or not.

15) Odometer

It is a scientific instrument that indicates the distance travelled

by a vehicle such as a car, motorcycle, etc. It can a mechanical or

electronic device or a combination of both, e.g.,

electromechanical odometer. It is generally located in the

dashboard of a vehicle.

The advanced electronic or digital odometer is provided with a

computer chip to measure the distance covered. The readings

are displayed digitally. A prototype odometer was built by

Benjamin Franklin in 1775, to measure the mileage of his carriage.

16) Ohmmeter

It is used to measure or calculate the electrical resistance of a circuit.

The unit of resistance is ohm, so it is measured in ohm. The

electrical resistance of a circuit or conductor indicates how much it

resists the flow of current through it.

17) Cathetometer

It is a scientific instrument which is used to measure the minute

differences in the levels of surfaces of liquids with great accuracy.

E.g., the distance between the levels of the mercury in the tube of a

barometer and in any other container such as a cistern, glass tube,

etc.

For example, the difference in the heights of the upper surfaces of

two columns one with mercury and another one with any other

liquid, or the same liquid in two columns at different times. It can

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also be used to check the difference in the levels of a liquid in dilatometer

due to a chemical reaction.

18) Colorimeter

Calorimeter is used to measure the absorbency of light waves. It is a light-

sensitive device that is used for measuring the absorbance of light passing

through a liquid sample.

Using a colorimeter, the amount of light travelling through a solution is

compared with the amount of light that can get through a sample of pure

solvent that does not contain the solute.

19) Crescograph

It is a device that is used to measure the growth in plants. It

was invented by Sir Jagadish Chandra Bose at the beginning of

the 20th century.

This main components of this instrument include a smoked

glass plate and clockwise gears. The plate is calibrated at

regular distance intervals to measure the growth or movement

of the tip or roots of a plant under observation at a magnification of up to 10,000 times.

20) Cryometer

It is a type of thermometer that is used to measure very low

temperatures of objects. There are lots of devices that can be

used as Cryometers.

These devices are mostly used to measure low temperature in

space.

21) Dilatometer

It is a scientific instrument that is developed to measure the

changes in the volume or length of a material that occurs as a

result of a change in temperature.

These materials can be ceramics, glasses, polymers, and

metals. These changes in the dimension of material are

measured on the basis of dilatometry.

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There can be many reasons for volume changes apart from temperature such as

absorption of fluids, chemical reactions, or mechanical stress such as pressure on a solid

object.

22) Electroscope

It is an instrument used to detect the presence of an electric charge

on a body. The first electroscope was developed by a British

physician William Gilbert in 1600. It had a pivoted needle and was

called versorium.

It works on the principle of Coulomb electrostatic force and is

comprised of a metal detector knob which is connected to a pair of

metal leaves.

In case of a positive charge in the object, the electrons in the electroscope's metal get

attracted to the charge and move upward out of the leaves that tend to build a

temporary positive charge in the leaves and as the same charges tend to repel each

other, the leaves get separated. On removing the charge, the electrons take their

original position and the leaves also come to their initial position.

In case the charge on the test object is negative, the electrons in the metal of the

electroscope repel and move toward the bottom of the leaves. This increases the

negative charge in the leaves temporarily again as same charges repel, the leaves will

separate again.

23) Ondometer

It is used to measure the wavelength and nature of the

electromagnetic radiations or waves. It is sometimes also called

wavemeter. The electromagnetic radiation is comprised of many

radiations of different wavelengths known as the electromagnetic

spectrum.

The radio waves are known to have the highest wavelength and

gamma rays are known to have the shortest wavelength. So,

ondometer is designed to distinguish the radiations on the basis

of their wavelengths.

24) Optometer

It is a device that tracks the path travelled by the light after it enters the eye. It is called

eye refraction. If the path travelled by light is not normal then it is known as a refractive

error that may be corrected using eyeglasses or contact lenses. Thus, Optometer helps

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assess a patient' vision by providing numbers as per the power of a person's vision. It is

widely used by optometrist or ophthalmologist in a clinical setting. The use of

Optometer is called optometry.

25) Otoscope

It is a specialized hand-held instrument used by physicians to

examine the ear more specifically the ear canal and eardrum.

However, it can also be used to examine the nose and throat

passages in the body.

Some otoscope can perform some specialized functions such as

pneumatic otoscopes that send a small puff of air to the eardrum to

check the vibration produced in the eardrum. It detects wax build-up in the ear canal or

a rupture in the eardrum.

26) Periscope

It is a device that is designed to observe over, or around an obstacle

that prevents the direct line of sight. It works on the principle of

laws of reflection of light. It consists of an outer body provided

with two mirrors at an angle of 45 degrees to each other so that

when light falls on one mirror, it is reflected back and falls on the

other mirror and gets reflected again towards the observer's eyes.

It is mostly used in land and sea warfare, submarine navigation. It

allows the user to see the surroundings while remaining hidden,

undercover, or behind armour or submerged in the water.

27) Phonograph

It is a device that is developed to reproduce the sound recorded on a grooved disc. It is

provided with a stylus or needle that vibrates while following a

spiral groove on the revolving disc to reproduce sound. It is also

known as a gramophone or disc player or a record player.

It works smoothly and is capable of producing a clean and high

sound. The phonograph was invented on 21 November 1877 by

Thomas Alva Edison and he got it patented on 19 February 1878.

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28) Polygraph

It is sometimes known as a lie-detector device. It is

typically used to test the physiological responses of a

person while replying to a set of yes or no questions related

to a crime, incident, and any other sensitive purpose. Its

objective is to check if a person is telling the truth or lying

while answering a set of questions. It is also performed on

a person applying for certain government jobs such as

while applying for a job in the FBI or CIA.

29) Pyrometer

It is a scientific device that is designed to measure relatively

high temperature such as in furnaces without touching and

where we cannot use ordinary thermometers. It is based on the

fact that every hot object emits heat or thermal radiations. So,

most of the pyrometers work by measuring heat radiations

emitted from the objects.

The basic design or components of a pyrometer include an

optical system and detectors. The optical system made of the

lens focuses on the heat radiations emitted by the object and collects the radiations then

sends them to the photodetector, which is sensitive to radiations. The detector then

analyses the energy level of the radiation and accordingly provides the output about the

temperature of the object. The first pyrometer device was invented by Josiah

Wedgwood.

30) RADAR

It stands for Radio Detection and Ranging. It is a

detection system that is used to determine the

location and distance of distant objects using radio

waves.

A standard radar system consists of an antenna to

transmit the radio signal or electromagnetic waves

in a particular direction and a receiver that detects

and receives the echoes that are reflected from the

target object that comes in the path of the radio signal. Based on the analysis of echoes

received, the position, location, distance and speed of the target object are calculated.

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Uses of Radar:

Radar can be used for various purposes, some of which are as follows:

To track and detect the position or presence of satellites, spacecraft, planets, and

other celestial bodies.

To navigate aircraft in the sky and ships in the water.

To control and manage the traffic in the air.

To find out the location of the fighter jets, helicopters, etc., of the enemy.

31) Rain Gauge

It is a simple scientific instrument that is used to measure the amount

of rain during a particular interval of time per unit area. It is also

known as ombrometer. The first standard rain gauge was invented in

Korea in 1441. Later, in 1661, Christopher Wren and Robert Hooke

developed the first tipping bucket rain gauge in Britain.

A standard Rain Gauge (Cylinder Ombrometer) is comprised of a

graduated cylinder that is placed in an open area to collect the

rainwater. During the rainfall, the water gets collected in the

cylinder. By noticing the level of water in the calibrated cylinder you can measure the

total rainfall.

32) Refractometer

It is a scientific instrument that is used to measure the refractive

index of a liquid or solid substance. It measures how much the light

bents or refracted when it enters into a substance from the air. It

measures the characteristics of liquids and solids using the light

refraction.

When it is used for liquids, it tells about their salinity, specific

gravity and fluid concentration, etc. This device is used in multiple industries e.g., in the

food and beverage industry by researchers and in the jewellery industry by gemmologist.

Uses of Refractometer:

Winemaking industry uses to measure the sugar content of grapes or other fruits.

Sugar companies use it to find out the percentage of sugar in syrups,

concentrated saps, etc.

Doctors use them to determine the concentration of proteins in blood samples.

It can be used to determine the salinity of a salt-water aquarium.

It is also used to identify a sample by comparing its refractive index to the

predefined refractive indexes of other substances.

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33) Sextant

It is used to find out the angle between the horizon and a

celestial body such as Stars, Moon, Sun, etc. It is a navigation

instrument that helps determine longitude and latitude, more

specifically the altitude of the sun, stars above the horizon.

So, it helps a navigator to find his position on the earth while

travelling in a ship. It has two mirrors, one is fixed on the

sextant' body and the other one is fixed on the index arm called

the pivot.

34) Seismograph

It is a scientific instrument developed to detect, measure or record earthquakes. It is

capable of recording the motion of the ground during an earthquake. Sometimes, it is

also called a seismometer. During an earthquake, seismic

waves are produced.

These propagating vibrations travel outward to all

directions carrying energy from the origin of an

earthquake. The record of vibrations produced by a

seismograph on a screen or a paper is called a

seismogram.

Using a seismograph, you can find out, the magnitude,

depth and location of the earthquake.

35) Speedometer

It is a device installed in the vehicles to measure their speed while

moving on the roads. It allows drivers to maintain a sensible and

safe pace. It indicates the speed in miles per hour, kilometres per

hour or both.

The first speedometer was invented by Charles Babbage, later the

more advanced electric speedometer was invented by Croatian

Josip Belusic in 1888, and it was called a velocimeter.

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36) Spherometer

A Spherometer is a scientific device that is developed to measure

the radius of curvature of spherical surfaces with great precision.

The radius of curvature of a curved mirror is the radius of the

sphere that was used to make the curved mirror.

For the first time, it was used by the opticians to measure the

curvatures of the spherical surfaces of the lens.

It is placed on the mirror whose radius of curvature is to be

measured.

It was French optician Robert Aglae Cauchoix who discovered the first known

Spherometer in 1810.

37) Sphygmomanometer

It is used to measure blood pressure in humans. The blood

pressure reading obtained by using a sphygmomanometer is

composed of two numbers that indicate systolic and diastolic

pressures. E.g. 120/80 mm Hg. The top number indicates the

systolic pressure in your arteries when your heart muscle

contracts.

Diastolic refers to the resting period between two heartbeats.

The contractions and relaxations of hear muscles cause

heartbeats that pushes blood into the arteries.

It causes a rise (during contractions) and a fall (during relaxations) in arterial blood

pressure. The highest arterial pressure during contractions is called systolic pressure

and it is followed by low blood pressure during the relaxation phase, which is called

diastolic pressure.

38) Stethoscope

It is a scientific instrument that is used by doctors to detect or listen

to the sounds produced in the body such as heartbeats and sounds

produced in lungs, intestinal tract including the sound of blood flow

in the peripheral vessels and the heart sounds of the foetus in the

womb of pregnant women. It is used for the proper diagnosis of a

patient's condition or illness. It is a binaural device, so it is used with both the ears.

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The stethoscope is most often used to detect the heart murmurs or abnormal heartbeats,

and to listen to the sound of air moving through the lungs to detect abnormalities in the

air tubes and air passages in the lungs. It was invented by French physician R.T.H.

Laennec in 1819.

39) Tachometer

It is used to measure the rotation speed of a rotating

object such as crankshaft of an engine. It measures

revolutions per minute performed by the object. A

tachometer is also known as a revolution counter. In

general, it comprises a dial and a needle to display the

readings related to safe and dangerous limits.

An engine is designed to spin within its limits or as per the piston's ability to pump the

crankshaft to spin. The tachometer counts the number of revolutions the crankshaft is

making in a minute. If the RPM is more than the allowed range, the moving parts will

produce heat and friction and will get damaged. So, a tachometer has been provided to

let the driver known the safe speed limits. There are various types of tachometers used

in vehicles.

40) Telemeter

It is used to measure the distance between two objects, which

may be moving or only one of them is moving and another one

is stationary.

It was developed for the first time by the army to find out the

distance of enemy camps based on the sound made by their

gunfire.

Even today it is used in the military in combination with other

technologies to find the range of enemy weapons and missiles.

Besides these applications, it can also be used in prediction of weather conditions,

tracking of bird and aquatic animals, exploring the space, and more.

Major uses of telemeter:

The electronic telemeters help fighter jets to estimate the distance of the fire of

enemies. It also helps to destroy the targets using missile lock-on; a process that

acquires a target and tracts it to guide the missile to hit it accurately.

It is used by space agencies to gather data and monitor satellite movements.

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It is used by the weather department to determine the time, speed and distance of

storms.

It is used by zoologists to track birds and sea creatures for analysing species and

migratory data.

41) Thermometer

It is a scientific device that is used to measure temperature. It can

be of different types as it can be used to measure the temperature of

a wide range of substances such as food, liquids, gases, air and

human body temperature.

The commonly used measurement units for the measurement of

temperature include Kelvin, Fahrenheit and Celsius.

Uses of thermometers:

It is used by doctors to check body temperature during fever or any other illness.

It can be used in the kitchen to measure the temperature of foods.

It is used in refrigerator and air conditioners to maintain a set temperature.

In factories, it is used to turn on and off the furnace. You are required to choose

the right type of thermometer that suits your

requirements.

42) Tonometer

Tonometer is used to measure the pressure inside the eyes of

a person. This internal pressure of the eye is known as the

intraocular pressure (IOP).

Tonometry is a test that is performed using a tonometer for the diagnosis of glaucoma, a

disease in which the fluid pressure inside the eye increases that may damage the optic

nerve.

The Goldman applanation tonometer is the commonly used tonometer by the doctors.

In Goldman tonometry, first anaesthetic eye drops are poured into the eyes then a small

amount of a fluorescein dye.

43) Venturimeter

It is a scientific device that is used to measure the speed and

rate of flow of a fluid that is flowing in a pipe. It works on

the principle of Bernoulli's equation that says as the velocity

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increases pressure decreases.

Although the principle of Venturimeter was introduced for the first time by G.D. Venturi

in 1797, it was considered with the support of C. Herschel in 1887.

Then water enters the throat whose area is uniform and least in the device. So, as the

water enters the throat its velocity and pressure remain the same that causes pressure

difference of the fluid at the two sections, which is noticed by the manometer and is

used to calculate the rate of flow through the Venturimeter.

44) Vernier Caliper

It is used to measure linear dimensions such as distance or

straight line between two points. It is an ideal measuring tool

to measure the diameter of spherical objects like pipes,

cylinders as the jaws of the caliper can be positioned on both

the sides of the circumference. It was invented by Pierre

Vernier in 1631.

It can be used for three types of measurements that include

outside distance such as length of an object, inside distance

such as width or diameter of a groove or hole, and depth of a hole or height of a step.

The accuracy of the Vernier scale also depends on the ability of a person to detect the

lines that are aligned and which are not aligned. The advanced calipers are digital as

they come with an LCD to display readings. It reduces the chances of error in reading

the scale.

45) Viscometer

It is an instrument which is used to measure the viscosity of a

fluid and semi-solid including the solid food products.

Viscosity is the fluid's resistance to flow. By measuring the

viscosity, the thickness or internal friction of a material can be

measured or quantified.

The units to measure viscosity are centipoise (cP) or Pascal-

sec (Pa-s). For example, the viscosity of water is one centipoise (cP).

A wide range of viscometers is available for a wide range of applications. Such as classic

capillary tube that lacks moving parts, and advanced hydraulic systems, Krebs-Stormer

viscometer, and more.

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Viscometers are very useful in quality assurance laboratories to check the flow

behaviour of materials caused by wrong processing, formulation, and staling, etc.

For example, it is widely used by food processing plants who are engaged in the

production of fruit juices, ketchup, jam, gums, syrups, mayonnaise, honey, and more.

46) Wattmeter

It is a professional, electric instrument that is used to measure

the flow of current or electricity or electric power through high-

voltage electricity lines.

Along with the flow of current, it also measures the voltage and

current values which can be used to calculate power in watts.

Wattmeters are mostly used in the transmission and

distribution of electric power. The most common type of

wattmeter is dynamometer type.

47) Wavemeter

Wavemeter, which is also known as wavelength meter, is a scientific

instrument that is used to measure the wavelength of laser beams

with great precision.

There are many types of wavemeter such as scanning wavemeters,

and static instruments without any moving parts.

A wavemeter is an interferometer that measures only wavelengths.

An interferometer measures wavelengths through interference using

mirrors, e.g., a beam of light is split into two and then it is recombined again.

The shape attained after it recombines is studied to take the measurement of the beam.

Generally, a wavemeter is typically of two types; scanning and static. The working of

scanning type is similar to Scanning Michelson Interferomete

48) Bolometer

It is a device used to detect and measure heat or electromagnetic

radiations of microwave energy. It was invented by Samuel

Pierpont Langley, who was an American astronomer. In the

beginning, it was used along with a telescope for quantifying

infrared radiation.

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It uses an element whose resistance changes with temperature, e.g., thermistor,

barretter, etc.

Barretter has a positive temperature coefficient, which means its resistance increases

with an increase in temperature. On the other hand, the temperature coefficient of the

thermistor is negative, which means its resistance decreases with the increases in

temperature.

49) Fluxmeter

It is a scientific instrument that is used to measure the flux

of a permanent magnet. In fact, this device is an advanced

version of the ballistic galvanometer with certain benefits

like heavy electromagnetic damping and low controlling

torque.

There are many advantages of using a fluxmeter such as it is

portable, its scale is calibrated in Weber meters, and the coil' deflection is not affected

by the time taken by flux to change.