Important Scientific Instruments and Their Uses Notes

Questions on scientific instruments appear again and again in SSC, railways, banking, defence and State service exams, and sometimes in the UPSC prelims as a part of science and technology. The question is usually simple: "Which instrument is used to measure ___?" But the names are similar, and students get confused between the barometer and the manometer or between the hygrometer and the hydrometer. This note lists the important scientific instruments with their uses, divided into groups, along with tricks to avoid confusion, the meaning of common prefixes, and practice questions. You can learn the units that these instruments use in our notes on SI units and measurement.

Why Are Instruments Important for the Exam?

Instrument questions are direct and need only one fact, so they are scoring. A student who learns around 60 instruments properly can answer all such questions in a few seconds. The questions come in three forms: (1) instrument to use, (2) use to instrument and (3) odd-one-out, where one instrument does not belong to the group. A good understanding of the word root helps in all three forms.

Weather and Measurement of Nature

Instruments of Measurement and Medicine

Optical Instruments

Other Important Instruments

Tricks to Avoid Confusion

• Barometer vs Manometer: The barometer measures the pressure of the atmosphere, while the manometer measures the pressure of a gas inside a closed container.
• Hygrometer vs Hydrometer: "Hygro" means moisture (humidity of air), while "hydro" means water or liquid (density of liquid).
• Odometer vs Speedometer: The speedometer shows how fast, and the odometer shows how far.
• Radar vs Sonar: Radar uses radio waves in air, sonar uses sound waves in water.
• Periscope vs Telescope: The periscope shows what is above the water, the telescope shows what is far away.
• Ammeter vs Voltmeter: The ammeter is connected in series, the voltmeter is connected in parallel.

Meaning of Common Word Parts

Many names can be decoded from their parts. The ending -meter means "to measure", the ending -scope means "to view or examine", and the ending -graph means "to record". So a thermometer measures heat, a microscope views small things, and a seismograph records earthquakes. The beginning baro- means pressure, hygro- means moisture, anemo- means wind, pluvio- means rain and seismo- means earthquake. If you remember these parts, even a new name can be guessed correctly. For some famous discoveries behind these devices, see our list of inventions and discoveries.

Instruments in the Daily Life of India

Several of these instruments are used by Indian institutions. The India Meteorological Department uses the barometer, anemometer, rain gauge and radar to give weather forecasts. ISRO uses the telescope in its space observatories. Hospitals use the stethoscope, sphygmomanometer, ECG and ultrasound scanner every day. The Indian Navy uses sonar to detect submarines, and the Indian Air Force uses radar for air defence. Linking an instrument to a real use makes the answer easy to remember.

How Some Important Instruments Work

Barometer. The simple mercury barometer, invented by Torricelli, has a glass tube filled with mercury and turned upside down in a bowl of mercury. The height of the mercury column shows the pressure of the air. When the mercury falls suddenly, it is a warning of a storm or rain, and when it rises slowly, the weather is going to be clear. The normal height at sea level is about 76 cm.

Thermometer. A clinical thermometer measures the temperature of the human body and has a small kink near the bulb, so that the mercury does not fall back by itself after the reading is taken. The normal body temperature is about 37 degrees Celsius, or 98.6 degrees Fahrenheit. Laboratory thermometers have a wider range, and a pyrometer is used when the temperature is too high for a normal thermometer.

Radar. The word radar stands for Radio Detection and Ranging. It sends radio waves, and when they strike an object such as an aircraft, they return as an echo. The time taken by the echo gives the distance, and the change in the frequency gives the speed. This is why radar is used by airports, the army and the weather department.

Sonar. The word sonar stands for Sound Navigation and Ranging. A ship sends ultrasonic waves into the water, and the echo from the sea bed or from a submarine is received. The depth is calculated from the time of the echo. Bats and dolphins also use this principle of echo location in nature.

Seismograph. It has a heavy mass that stays still when the ground shakes, and a pen that records the movement on paper or on a screen. The strength of the earthquake is expressed on the Richter scale, and the point on the surface directly above the origin of the earthquake is called the epicentre.

Instruments Linked With Units and Scales

Examiners like to link an instrument with a scale or a unit. The Richter scale is used for earthquakes, the Beaufort scale for the force of wind, the Mohs scale for the hardness of minerals, the decibel for the loudness of sound, the Celsius, Fahrenheit and Kelvin scales for temperature, and the pH scale for acidity. Blood pressure is written in millimetres of mercury, such as 120 over 80, where the higher value is the systolic pressure and the lower is the diastolic pressure. Atmospheric pressure is measured in millibar or hectopascal. Keeping these links in mind will help you in the questions that ask both about the instrument and about the quantity.

Common Mistakes

Students often write "thermometer" for every temperature question, but it is a pyrometer which is used for the very hot objects such as a furnace. Some students think that the stethoscope measures the heart beat, but it is only used to listen to the sounds, whereas the ECG records the electrical activity. Some also confuse the telescope with the periscope, or the Geiger counter with the cyclotron. A careful look at the word root and the field of use will remove these errors. Another common error is to mix up the inventor with the instrument, for example, to think that Galileo invented the barometer. He did not, as Torricelli did.

Link With Other Subjects

Scientific instruments are not a separate topic. They connect with physics (pressure, light, sound), biology and medicine (blood pressure, heart and brain tests), geography (weather and the study of earthquakes), and defence (radar and sonar). When you study climate or earthquakes in geography, remember the instrument used. When you study the human body, remember the test and the instrument for it. This way, one topic is revised many times without any extra effort.

How to Revise

1. Prepare a two-column sheet of instrument and use, and test yourself by covering one column.
2. Study the instruments in the groups given above, instead of an alphabetical list.
3. Revise the confusing pairs twice a week.
4. Solve previous year questions from SSC and railway exams to see the pattern.

Practice Questions With Answers

• Q1. Which instrument measures the humidity of air? Answer: Hygrometer.
• Q2. Sonar is used to detect objects using which waves? Answer: Sound waves.
• Q3. Which instrument is used to measure blood pressure? Answer: Sphygmomanometer.
• Q4. What does a lactometer measure? Answer: The purity of milk.
• Q5. Which instrument records the electrical activity of the heart? Answer: Electrocardiograph (ECG).

Quick Revision

• -meter measures, -scope views, -graph records.
• Barometer: air pressure; manometer: gas pressure; hygrometer: humidity; hydrometer: liquid density.
• Radar uses radio waves; sonar uses sound waves.

Frequently Asked Questions (FAQ)

What does a barometer measure?

A barometer measures the atmospheric pressure.

What is the use of a hygrometer?

A hygrometer measures the humidity of the air.

What does an anemometer measure?

An anemometer measures the speed of the wind.

What is a sphygmomanometer used for?

It is used to measure blood pressure.

What is the difference between radar and sonar?

Radar uses radio waves to detect objects in air, while sonar uses sound waves to detect objects under water.

What does a lactometer measure?

A lactometer measures the purity of milk.

What does a seismograph do?

A seismograph records the intensity and waves of an earthquake.

What is a pyrometer used for?

A pyrometer is used to measure very high temperatures.

What does the ending -scope mean in instrument names?

The ending -scope means to view or examine, as in microscope and telescope.

Which instrument measures the depth of the sea?

The fathometer measures the depth of the sea.

What does a Geiger counter detect?

A Geiger counter detects radioactivity.

How should I prepare instruments for the exam?

Learn them in groups, use word roots, revise confusing pairs and solve previous year questions.