Overview

The lie detector flails wildly, "He's guilty!" Did you ever wonder how a machine could tell if someone was lying? Simple. It uses a sensor. A sensor can detect a stimulus by using a chemical or physical reaction. Sensors are very perceptive and are capable of responding to environmental factors that may be indiscernible to the human senses. They have become a vital part of our everyday lives.

Why This Science Matters

In an increasingly complex society, the role of sensors in our lives has risen greatly, from simple sensors that detect water, to more complicated sensors that recognize explosives from potential terrorists. People use their senses, sight, touch, sound, smell and taste, to become aware of their environment. It prevents us from burning our finger or crossing the street into oncoming traffic. What if we can't detect a warning, using these methods? Sensors work the same way as our senses, only they can be more sophisticated. They detect water flooding a basement, toxic carbon monoxide fumes filling a garage or nerve gas released in a crowded room. Sensors can be used to help and protect us.

Chemical sensors use two methods, electrical and optical, to gain information or detect danger. Electrical sensors, such as a voltmeter, measure conductivity with a capacitor. An optical sensor, such as a carbon monoxide detector, has chemicals that change color when exposed to certain elements. These inventions are providing a safer, more communicative alliance with our ever-changing, dynamic environment.

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Explore This Topic

The following questions accompany this lesson. The answers are given below each question. To reveal an answer, place the cursor over "REVEAL THE ANSWER".

1. What is a voltmeter?

2. What is an ohm?

3. What is a capacitor?

4. What is resistance?

5. What is a conductor?

6. What is an electric circuit?

7. How do lie detectors work?

8. How do carbon monoxide detectors work?

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Links & Resources

Mike Sailor at UCSD
The fascinating research explored in Mike Sailor's Lab.

Movies and articles about sensors
Movies and articles about different sensors developed in Mike Sailor's Lab at UCSD, including one to detect small amounts of TNT and another to detect nerve gas.

PDF Document: Building Your Own Sensor
Directions to build your own humidity sensor (voltmeter).

"Medical Detection of False Witnesses" by Brandon Spun
Insight on the News, Feb. 4, 2002, vol.18, issue 4. This journal article describes how high tech lie detectors may be impossible to fool, but they still stir up controversy.

"Lie-Tech" by Nicole Dyer
Science World, Oct. 1, 2001, vol. 58, issue 3, p.4. This journal article questions whether brain fingerprinting can improve on chemical sensors as lie detectors.

A Tremor in the Blood: Uses and Abuses of the Lie Detector by David Thoreson Lykken
New York: Plenum Trade, 1998. This book discusses how effective lie detectors are.

"Bioterror Detection Device Developed"
Drug Discovery and Technology News, Dec., 2001, vol.4, issue 12. This journal article describes how living cells are used to detect and identify chemical and biological warfare threats like anthrax, bolulinum and neurotoxin

"Chemical Sensors Gain True Portability"
Science News, Aug.18, 2001, vol. 160, issue 7, p. 103. This journal article explains how novel films change color on contact with selected chemicals, like nerve gas or rotting fish. It's a step towards warning badges for military personnel or spoilage indicators for supermarket items.

"Plume-Tracking Robots: A New Application of Chemical Sensors"
The Biological Bulletin, April, 2001, vol. 200, issue 2, p.222. This journal article shows how robots have the potential to find and search for hazardous chemicals and pollutants.

"Evanescent Wave Films for Chemical Sensing" by Frost and Sullivan
Advanced Coating and Surface Technology, June 1, 2001, vol. 14, issue 6, p.7. This journal article details how sensors on membranes can directly detect and absorb target chemicals from water.

"Chemical Odor Sensor for Use in Land Mine Detection"
All Hands, July 2001, Innovators. Office of Naval Research. p. 12. This journal article describes an electronic nose that is so sensitive, it has 20 attributes of the living nose.

"New Optical Methane Detector Improves Gas Leaks Survey"
Pipe Line and Gas Industry, Sept., 2000, vol. 83, issue 9, p. 26. This journal article tells about a vehicle mounted device that accurately detects natural gas five times faster than conventional methods.

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Lesson developed by Leigh Morioka, fifth grade science teacher at Dingeman Elementary, San Diego Unified School District.