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Explanation of Sensors and Detectors - Succeed in Physical Science. Also refer to physics, chemistry, senses, sight, hearing, smell, taste, touch, plants, animals, light, heat, pressure, electricity, radio, television, amplifier, filter, Ron Kurtus, School for Champions. Copyright © Restrictions

Sensors and Detectors

by Ron Kurtus (revised 27 March 2007)

A sensor or a detector is a device that responds to a stimulus, such as heat, light, or pressure. It then generates a signal that can be measured or interpreted. Humans, animals and even plants have sensors that can detect the world around them. Detectors are used in physical science to respond to energy signals and forces. They are necessary for measurements and experiments. Signals can be manipulated to make their information more usable.

Questions you may have include:

• What sensors are used in living things?
• What sensors or detectors are used in science?
• How can signals be manipulated?

This lesson will answer those questions. There is a mini-quiz near the end of the lesson.

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Living sensors

Humans, animals and plants have sensors that detect signals from the world around them.

Humans and animals

Humans and animals can detect various forms of energy through their sensors or detectors:

• Eye detects light energy
• Ear detects sound energy
• Skin detects both physical pressure and heat energy
• Nose detects certain chemical reactions
• Tongue detects other chemical reactions
• Inner ear detects gravity

Some animals can also detect electrical signals and magnetic fields.

(See Using Your Senses for more information on this subject.)

Plants

Plants have the ability to detect or sense various forms of energy. They detect light, heat, touch, certain chemicals, and gravity. Examples include:

• Flowers open when the sun shines.
• Seeds react to warm weather.
• A Venus Flytrap detects the pressure of small insects.
• Roots will avoid toxic materials in the ground.
• Plants grow in the opposite direction of gravity.

Detectors in science

In order to study anything in science, you must first be able to detect it. The most interesting things, of course, are those that we can detect with our own senses. We then use devices to amplify what we can sense, in order to study those energy forms more thoroughly.

We also use detectors to study energy forms that we are not able to sense, such as magnetic fields. Detectors and sensors make up the starting point for most scientific studies.

Man-made detectors

Scientists have invented various types of sensors to detect energy forms. For example, a smoke detector in you home will set off an alarm when the energy from smoke or heat reaches its detection device. The microphone on you tape recorder detects the energy from sound waves and creates an electric signal that records the sound.

• Solar cells and photographic film detect light.
• Microphones detect sound.
• Thermometers sense the change in heat or temperature.
• Pressure gauges detect touch.
• Scales detect and measure the effect of gravity.
• There are many devices that detect various chemicals and even odors.
• A magnetometer detects magnetic fields.
• An electric meter detects electricity.
• A Geiger counter detects atomic radiation.

Changing signals

The signals received by a detector may often be manipulated to gather desired information. Often the signal received is weak, so it must be amplified. Sometimes the signal is too strong, so it must be filtered. Extraneous signals and noise also must sometimes be filtered out, so that only the desired signal comes through.

Amplifiers

Besides detecting energy forms, many devices amplify or enlarge the signal. Some are mechanical, but most amplifiers are now electronic. Examples of amplifiers include:

• A telescope makes distant objects appear closer.
• Electronic amplifiers can increase the level of sound
• Very faint chemical signals (odors or tastes) can be amplified electronically to give their details.

Filtering

If you would try to study the Sun, the light would be too bright to view or photograph. A filter could be used to lower the light level. It could also filter out all colors except those that you want to measure.

Sometimes electrical signals on the radio or television include static and other forms of noise. Electronic filters eliminate the noise and allow you to get a good, clear signal.

Summary

A sensor or a detector is a device that responds to a stimulus or form of energy. It then generates a signal that can be measured or interpreted. Humans, animals and even plants have sensors that can detect the world around them. Detectors are used in physical science to respond to energy signals and forces. They are necessary for measurements and experiments. Signals can be manipulated to make their information more usable.

Answers to Readers' Questions

Observe the world around you

Resources

The following resources provide information on this subject:

Websites

Physical Science Resources

Books

Top-rated books on Physical Science

Miscellaneous

Mini-quiz to check your understanding

1. What animals detect electric signals?

2. Why do we need scientific devices to detect things?

3. How are radio waves detected?

If you got all three correct, you are on your way to becoming a Champion in Physical Science. If you had problems, you had better look over the material again.

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