Monitoring & control (Cambridge International AS Computer Science)

Monitoring vs control

Monitoring systems

• A monitoring system is used to collect data continuously through observation

• It works by passively gathering data

• It does not interact with or change the environment

• The system does not take action based on the data collected

• Designed for high accuracy using precise sensors and measurements

• Examples of monitoring systems include:

  • Weather stations
  • Patient monitoring in hospitals

Weather stations

• Collect data like temperature, wind speed, humidity, and rainfall
• Used by meteorologists to observe and predict weather patterns
• Data is collected 24/7 but the system does not react or change anything

Patient monitoring

• Tracks heart rate, oxygen levels, and blood pressure in real-time
• Alerts medical staff if readings go outside safe ranges
• The system itself just records and displays data, it doesn’t directly treat the patient

Control systems

• A control system is used to automatically manage or adjust a process based on data collected from sensors

• It works by monitoring input, then taking action if certain conditions are met

• Unlike monitoring systems, control systems do interact with the environment

• They are designed to keep systems stable, safe, or working efficiently without human input

• Examples of control systems include:

  • Central heating system
  • Automatic irrigation system

Central heating system

• Monitors room temperature using a thermostat
• If the temperature drops below the set level, the boiler is switched on
• Once the target temperature is reached, the system turns the heating off automatically
• The system constantly checks and adjusts to maintain the desired temperature

Automatic irrigation system

• Monitors soil moisture levels in farmland or gardens
• If moisture drops too low, it activates sprinklers to water the plants
• Once the soil reaches the correct level, the system turns off the water supply
• Ensures plants are watered efficiently without wasting resources

Exam Hint

• Actuators are output devices in a control system that carry out actions based on data from sensors
• Examples include motors, heaters, valves, and pumps

Use of sensors

What are sensors?

• Sensors are input devices
• They measure a physical property of their environment such as light levels, temperature or movement
• Sensors can be used for both monitoring and control systems
• A process where outputs are recycled and used as inputs, creating a continuous cycle is called a feedback loop

Feedback loops

What is a feedback loop?

• A feedback loop is when a control system uses its output to influence its next input
• Allows the system to automatically adjust and stay within set conditions
• Feedback allows the system to check if it’s working as expected
• The output affects the next input, helping the system make adjustments
• This means the system can automatically respond to changes in its environment
• Helps the system stay within set limits or target values (e.g. temperature, moisture)
• Makes the system more accurate and efficient without needing human control

Example: Central heating system

• The system uses a thermostat to monitor the room temperature

• If the room gets too cold, the system turns the heating on

• Once the room reaches the set temperature, the system turns the heating off

• This process uses feedback:

  • The output (room temperature) affects the input (whether heating is needed)

• Feedback ensures the system automatically adjusts to keep the room at the right temperature

• No need for manual control as the system self-corrects using feedback