Computers can measure — Computing, 4–6
A sensor lets a computer turn something in the world into information it can use. Computing, 4–6 years.
A sensor notices a change
A sensor is a part that notices something, such as light, warmth, movement or sound. It sends a number or signal to a computer. The computer cannot feel like you do; it uses that signal to work out what is happening.
Why make a measurement?
A computer needs information before it can react to the world. A thermometer sensor can tell whether a room is warmer or cooler, and a light sensor can tell whether a lamp is needed. Measuring gives a program something to use instead of making a blind guess.
A lamp measures light
Suppose a sensor gives 2 in a dark room and 8 in a bright room. The program sets a limit of 4. First, it reads the sensor. Next, it compares the number with 4. If the reading is 2, it turns the lamp on; if it is 8, it leaves the lamp off.
A sensor is not a perfect sense
It is reasonable to think that a sensor knows exactly what you know, because both can notice light or sound. But a sensor has a limited range and can be confused by reflections, distance or noise. Check what it measures and how carefully before trusting its number.
Measurements in real devices
Automatic lights, washing machines and digital thermometers use measurements. A fitness watch measures movement, while a phone can measure its tilt to turn the screen. These devices do not understand the whole situation; they use particular measurements for particular jobs.
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