Electronic Systems, Control and Communication
What the domain tests
This domain examines block-diagram thinking: sensors, controllers, actuators, feedback, and communication from transmitter to receiver. You should distinguish open-loop and closed-loop systems, explain modulation, and recognise noise and bandwidth effects.
Core rules
- Open-loop control does not measure output; closed-loop compares feedback with a setpoint and acts on the error.
- Sensors convert physical variables to electrical signals; actuators convert control signals to action. Signal conditioning may include amplification, filtering and ADC/DAC conversion.
- Negative feedback reduces error and sensitivity to disturbance, but too much gain can cause instability.
- Communication chain: source, encoder/modulator, transmitter, channel, receiver, demodulator, destination. AM varies amplitude; FM varies frequency and is generally more noise-resistant.
Worked example
A heater control has a setpoint of 60 °C and a measured temperature of 55 °C. Error = setpoint − measurement = 5 °C. With proportional gain 2 output units per °C, the controller output increases by 10 units. If the heater raises temperature by 0.5 °C per output unit, the correction tends toward 5 °C. The sensor must be placed where it represents the controlled space, otherwise feedback is misleading.
Traps that cost marks
Reversing the feedback sign turns negative feedback into positive feedback. Open-loop systems cannot correct for disturbance. Do not confuse modulation with amplification. In communication, noise and bandwidth trade off against signal quality.