Monitoring and control systems

Overview of monitoring and control

show understanding of the difference between a monitoring system and a control system
show understanding of sensors and actuators and their usage
show understanding of the additional hardware required to build these systems
show understanding of the software requirements of these systems
show understanding of the importance of feedback in a control system

Monitor physical properties through the use of sensors and microprocessor
Usually monitor system is active 24/7, and data is captured continuously
One example is the observatory. They monitor the weather information and store all the recorded data for analysis

Smoke detector system is another example for monitoring
The sensor (particle sensor) will monitor 24/7 and if there's abnormality, the alarm may sound

From the above two examples, we can see there are mainly two reasons for monitoring system:
- Check the monitored value (physical property) is within acceptable range, if not, some form of immediate action is required
- Monitor the value and store data for future analysis

Control system is very similar to monitoring system, the difference is control system will attempt to regulate the monitored physical property
For example, an automatic heater (room) requires sensors to monitor the temperature of the room, but also regulate the temperature with the use of actuators (the heating element)

Key components in a typical control application

Microprocessor

Sensors

Actuators

ADC

DAC

Controlled Environment

Feedback

Analog signal

Digital data

Digital control signal

For the diagram in the previous page, sensor and actuator are situated in the same environment
e.g. Automatic heater, sensor will read the temperature of the room while actuator outputs (as heat) to the same room
The actuator output will change what the sensor will read, e.g. when heater turns on, temperature sensor may read a higher temperature; thus, we call this as Feedback to the system
Note the feedback is not directly done by connecting actuator to sensor, but indirectly through the monitored environment.

In Open loop system, the control is purely determined by the preset input. E.g.
- In an electric fan, the speed dial is the preset (by human input), and the output is how much power giving to the motor
- The motor speed is not very precisely controlled
In Closed loop system, preset input sets a target, but the control is determined by the sensor readings. E.g.
- In the Cruise control of a car, where speed of the car is maintained automatically
- Speed of car is not proportional to Power
- Sensor (speed) will use as well to maintain the power of output

show understanding of how bit manipulation can be used to monitor/control a device
carry out bit manipulation operations: test a bit and set a bit (using bit masking)
show understanding of how to make use of appropriate bit manipulation in monitoring systems and control systems