Input Devices

• All input devices transfer data from the source in the outside world to the computer. Some input devices require greater human intervention than scanners or cameras to generate the data. These include:

  • keyboards and keypads
  • pointing devices
  • microphones
  • touch screens
• The most common examples of pointing devices include:

  • mouse and tracker ball

  The actual device itself remains stationary
• There are 2 common types of barcodes:

  • UPC-A which is used in retail and warehousing, it can only represent numeric digits.
  • Code 128 which is used in transport and shipment tracking, it can represent both numeric digits and letters.
• Barcode readers use optical sensors that scan the bars on the label and convert them into digital signals that can be read by computers.
• QR codes are 2D barcodes the contain:

  • links to websites
  • information
• 2D Scanners are used to convert a hard/paper copy of a document or photograph into a computer-readable format
• Security cameras may use face recognition which is specialist software that measures and compares the proportions of a person's face with those stored. It may compare things such as:

  • distance between the eyes
  • shape of the cheek bones
  • width of the nose
  • length of the jaw line
• 3D scanners are used in both industrial and medical fields. They rely on a technology called tomography which means to image something in very thin slices.
• Some data can be obtained directly through sensors. Sensors often collect data in an analogue form an require conversion to digital data to be processed. They are used in both monitoring and control applications.
• A sensor is a device that detects changes in its environment, converts these changes into electrical signals and sends them to a microprocessor for processing.
• Analogue measurements are when the data has no discrete value and the data changes smoothly rather than in exact jumps.
• Types of sensors include:

  • Gas
  • Infra-red
  • Light
  • Temperature
  • Pressure
  • pH
  • Magnetic field
• Monitoring


  With these applications, the computer or microprocessor will make no changes to the actual process; it will simply report the values.
• Control

  • The output from the computer or microprocessor can alter how the process is operating;
  • it can change the value of the next input received by, for example, opening a valve, switching off a heater or changing the speed of a pump
  • the output from the computer or microprocessor can affect the next input it receives
• There are 3 different types of Detection Systems:

  • Pressure sensors - monitor an intruder stepping on the floor next to windows, doors or on the floor next to valuable paintings
  • Acoustic sensors - pick up the sound of breaking glass or footsteps on the floor
  • Infra-red sensors - pick up movement in the rooms but also changes in heat
• Detection systems work by the system first being activated by the use keying in a PIN code or by placing an alarm fob near a receiver. Data is converted into digital form using an ADC and is sent to a microprocessor.