Input devices

Question 1

Define

input device

Answer 1

Devices which are used to input data and instructions into a computer.

Input devices allow us to enter raw data into a computer. The computer processes the data and then produces outputs that we can understand using an output device. Input devices can be manual or automatic.

Question 2

How does a 2D scanner work and where may it be used?

Answer 2

• Mechanically scans illuminated surface of paper document with a single row of hundreds of light sensors
• Scanner computer digitises analogue signals, processes and sends to computer
• Flatbed scanner – paper document places on glass ‘platen’.
• Saved as image
• OCR software can convert images into text data which can be edited by a word processor
• May be used in offices to scan documents

Question 3

List some advantages and diadvantages of 2D scanners

Answer 3

Advantages:

• Flat-bed scanners are very accurate and can produce images with a far higher resolution than a digital camera

Disadvantages:

• Can produce very large image files which need a lot of computer memory to view and edit

Question 4

What is a 3D scanner, how does it work and where may it be used?

Answer 4

• A 3D scanner is a device that analyses a real-world object or environment to collect data on its shape and possibly its appearance (i.e. colour). The collected data can then be used to construct digital three-dimensional models.
• Contact scanners probe object
• Non-contact scanners use light or radiation, detects reflection or radiation passed through objects
• May be used by architects to scan scale models of projects

Question 5

List some advantages and disadvantages of 3D scanners

Answer 5

Advantages:

• industrial computed tomography scanning can be used to construct digital 3D models, applying non-destructive testing

Disadvantages:

• many limitations in the kind of objects that can be digitized
• optical technologies encounter many difficulties with shiny, mirroring or transparent objects

Question 6

How does a barcode scanner work and where may it be used?

Answer 6

• Barcodes consist of short parallel lines in contrasting colours and different thicknesses
• Reflected laser light detects differences in lines
• Combination of scanner hardware & software
• Processor and decoding software in scanner
• ID codes used to look up description & price in database
• Used for identification of items
• Commonly used in shops to scan items or airports to scan boarding passes

Question 7

List some advantages and disadvantages of barcode readers

Answer 7

Advantages:

• saves time (automatic inventory)
• are efficient in recording information
• durable

Disadvantages:

• cannot read damaged or obscured barcodes

Question 8

How does a digital camera work and where may it be used?

Answer 8

• Grid of light sensors that pick up optical image
• Computer scans analogue signal, digitises data and displays on monitor screen
• When user presses shutter button, shutter opens to let in light
• Stores data as image file in memory

Question 9

List some advantages and disadvantages of digital cameras

Answer 9

Advantages:

• No cost to purchase and process film
• Display acts as viewfinder
• No processing delay: can view and delete immediately
• Easier and quicker to edit
• Easily sent over network

Disadvantages:

• Uses a lot of power
• Small handheld digital cameras cannot store many photos.
• A corrupted memory card may result in lost photos.
• Cost - top specification digital cameras can be far more expensive than their equivalent roll film cameras

Question 10

How does a keyboard work and where may it be used?

Answer 10

• A user enters values and commands into a computer by pressing keys on a keyboard
• A standard keyboard each key has a value printed on it
• Users of English usually type on a QWERTY keyboard, named from the first 6 letters on the first row
• A concept keyboard consists of rectangular grid of keys. A flat overlay sheet covers the keyboard. It has a suitable picture, symbol or word for each key. Often used in restaurants.
• A numeric keyboard: A rectangular block of keys with the numerals 0 to 9. Can be used for inputting PINs when we pay by credit card, on mobile phones, or on keyboards next to the QWERTY layout.

Question 11

List some advantages and disadvantages of keyboards

Answer 11

Advantages:

• simple, familiar, reliable technology (typewriters used the same QWERTY layout)

Disadvantages:

• It is slower as human operator takes more time in thinking and typing.
• Only one letter can be typed at a time.
• Slow compared with devices for automatic data capture.
• Prone to vandalism in public locations

Question 12

How does a mouse work and where may it be used?

Answer 12

• Allows user to point by moving a cursor
• User selects items by clicking switch buttons on mouse
• A mechanical mouse has a small ball underneath that can roll over a flat surface. The mouse detects and converts the rotations of the ball in two dimensions into digital signals.
• An optical mouse has no moving parts, detects movement by changes in reflected light
• Used with a graphical user interface (GUI)

Question 13

List some advantages and disadvantages of using a mouse

Answer 13

Advantages:

• Fast method on inputting commands, feels natural
• Moves the cursor faster than the arrow keys of keyboard

Disadvantages:

• Needs flat surface on which to operate, can be easily vandalised
• Hard to use by people with physical disabilities
• Not always suitable to carry around, especially with PCs
• Picks up dust and dirt easily - ball may become stuck
• Textual data can’t be input

Question 14

How does a touch screen work and where may it be used?

Answer 14

• Screen is sensitive to the touch of a finger or stylus
• Three types of systems to recognize touch: resistive, capacitive, and surface acoustic wave
• Resistive system consists of glass panel covered with a conductive and a resistive metallic layer. When the user touches the screen and the layers make contact the electric current running through the layers changes. The change in the electric field is used to calculate where the screen was touched.
• Capacitive system has a layer storing electrical charge placed on monitor’s glass panel. Charge is transferred to user’s finger, and the charge decrease is detected and used to calculate where the screen was touched.
• Surface acoustic wave system consists of two transducers (one receiving, one sending) placed along the x & y axes of the monitor’s glass panel, along with reflectors to reflect an electrical signal sent between the transducers. The receiving transducer can tell if the signal was disturbed by touch.
• Used in phones, portable gaming consoles, Point-Of-Sale terminals, tourist information kiosks and systems to find out about public transport.

Question 15

List some advantages and disadvantages of touch screens

Answer 15

Advantages:

• Difficult to vandalize
• Don’t need separate keyboards or mice which can be stolen
• Can be made reasonably weatherproof
• Users need no previous computer knowledge to be able to use them, feels intuitive
• Less prone to malfunction due to dust and dirt
• Combines output device (screen) with input device so reduced space requirements
• Makes use of finger gestures, such as pinch to zoom

Disadvantages:

• People with disabilities may find them difficult to use
• Not suitable for inputing large amounts of data
• Long periods of usage can be tiring
• Generally more expensive

Question 16

How does a microphone work and where may it be used?

Answer 16

• Converts sound vibrations into an analogue signal.
• Usually connect the microphone’s signal to the computers sound card with a cable
• Diaphragm in microphone vibrates with sound. This may move a magnet or coil that induces current to flow in the wire.
• Used in phones, webcams, and laptops for adding sound to a multimedia presentation, mixing music and video conferencing

Question 17

List some advantages and disadvantages of microphones

Answer 17

Advantages:

• Voice recognition software can be used to convert your voice into text or to control menu options on a phone system

Disadvantages:

• Stored audio files can take up a lot of memory
• Voice commands can be difficult to recognise by the software

Question 18

What is a sensor, and why are they used?

Answer 18

• A sensor is a device that produces an electrical signal in response to a stimulus.
• Detects or measures a physical property and usually sends the data to a computer which can then record, indicate, or otherwise respond to it
• Can collect data more frequently, accurately and reliably than a person
• Can collect data from places unsafe for humans, e.g. lava flows, nuclear reaction vessels

Question 19

Describe how a light sensor can be used to input data into a computer system, and how it is used in real-life scenarios

Answer 19

• Produces a signal that depends on the level of light falling on it.
• Can be used as an input to an automated system that controls a device’s level of light output, e.g. the brightness of headlights, streetlights, or screens.

Question 20

Describe how a temperature sensor can be used to input data into a computer system, and how it is used in real-life scenarios

Answer 20

• Produces a signal that depends on the temperature of its surroundings.
• The computer processes the digitized signal to display a measurement or to control an appliance.
• Used in electronic thermometers or thermometers in controlling heating systems in buildings including greenhouses and chemical reaction vessels.

Question 21

Describe how a magnetic field sensor can be used to input data into a computer system, and how it is used in real-life scenarios

Answer 21

• Produces a signal depending on the magnetic field surrounding it
• Can detect changes and disturbances in a magnetic field like flux, strength and direction. Rotation, angles, direction, presence and electrical current can all be monitored.
• Magnetic sensors are divided into two groups, those that measure the complete magnetic field and those that measure vector components of the field. The vector components are the individual points of the magnetic field. The techniques used to create these sensors involve various combinations of physics and electronics.
• Can be used to detect the earth’s magnetic field, or smaller magnetic fields
• Used for compassing in cell phones and handheld GPS receivers, as well as in vehicles.
• Also used in industrial processes and scientific measuring

Question 22

Describe how a gas sensor can be used to input data into a computer system, and how it is used in real-life scenarios

Answer 22

• Produces a signal depending on the concentration of a particular gas or vapour
• Used in breathalysers, environmental monitoring and chemical process control

Question 23

Describe how a pressure sensor can be used to input data into a computer system, and how it is used in real-life scenarios

Answer 23

• Produces a signal depending on the pressure to which it is exposed
• Used in blood pressure monitors, chemical reaction vessels and robots

Question 24

Describe how a moisture sensor can be used to input data into a computer system, and how it is used in real-life scenarios

Answer 24

• Produces a signal depending on how wet it its surroundings are
• Used in irrigation systems to measure water ocncentration in soil

Question 25

Describe how a humidity sensor can be used to input data into a computer system, and how it is used in real-life scenarios

Answer 25

* Produces a signal depending on the concentration of water vapour in the atmosphere * Can be used in greenhouses, for controlling heating, ventilating and air conditioning systems, or for recording information for weather records

Question 26

Describe how a pH/acidity/alkalinity sensor sensor can be used to input data into a computer system, and how it is used in real-life scenarios

Answer 26

* The pH meter has a rod-like probe, usually made of glass, with a bulb at the bottom which contains the sensor. * The probe produces different voltages at different pH levels; theoretically producing 0 volts at pH 7 (neutral), negative voltages at acid pH levels and positive voltages at alkaline pH levels. * Used in chemical and pharmaceutical manufacturing, as well as in schools for lab experiments

Question 27

Describe how a motion/infra-red sensor can be used to input data into a computer system, and how it is used in real-life scenarios

Answer 27

* Produces signal depending on the level of infrared radiation falling on it * Infrared radiation may be detected by temperature differences (using the thermoelectric effect), pyroelectricity (where materials are able to generate a temporary voltage depending on temperature), or changes in resistance. * A change in an area’s infrared radiation is detected as movement. * Used in alarm systems, remote controls, weather monitors and sensor-operated traffic lights.