Cambridge A-Level ICT: Monitoring and Control — Practice Questions

These are original practice questions written in the style of Cambridge AS & A Level ICT (9626) assessment objectives. They are not taken from any past paper and are not endorsed by Cambridge International.

Use these questions alongside the Section 3 – Monitoring and Control study guide and revision notes.

Section A

1. State the key difference between monitoring and control. [2]

2. Name the three types of calibration. [3]

3. State the difference between a sensor and an actuator. [2]

4. Name two named actions or movements an actuator can carry out. [2]

5. Name three microprocessor-controlled systems listed in the syllabus. [3]

Section B

6. A weather station records humidity and atmospheric pressure throughout the day for a meteorologist to review later.

(a) Explain why this is an example of monitoring rather than control. [2] (b) Suggest what would need to change for this to become a control system instead. [2]

7. A sensor manufacturer tests a new temperature sensor and finds its readings drift slightly out of true over time.

(a) Explain why two-point calibration would be more suitable than one-point calibration for correcting this sensor. [2] (b) Suggest a situation where multipoint calibration would be needed instead of two-point calibration. [2]

8. A burglar alarm system uses an infrared sensor and a sound sensor together.

(a) Explain why an infrared sensor is well suited to detecting an intruder. [2] (b) Suggest one reason the system might use two sensor types together rather than relying on one alone. [2]

9. A central heating system automatically switches the boiler on when room temperature falls below a set point, and off again once the room warms up.

(a) Describe this system as a sensor → microprocessor → actuator chain. [3] (b) Explain why this system must be a closed loop, and what would be wrong with a system that only checked the temperature once. [2]

10. A car park barrier system uses a light sensor to detect a vehicle and a motorised actuator to raise the barrier.

(a) Represent this system’s logic as a simple flowchart description, including a decision box. [3] (b) Explain why the syllabus expects control processing to be represented as an algorithm or flowchart. [1]

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Answers

1. Monitoring reads and records a value for a human or system to review; control uses a sensor reading to trigger an automatic response without waiting for a human decision [2].

2. One-point, two-point and multipoint calibration [3].

3. A sensor takes a reading from the physical world; an actuator produces physical movement or action in response to a signal [2].

4. Any two of: linear, rotary, soft, hydraulic, pneumatic, electric, thermal, magnetic, mechanical [2].

5. Any three of: greenhouses, central heating systems, air conditioning systems, burglar alarms, control of traffic and pedestrian flow, car park barriers, traffic lights, wireless sensor and actuator networks, smart homes [3].

6. (a) This is monitoring because the sensor readings are being recorded for a human (the meteorologist) to review and interpret later, rather than automatically triggering an action [2]. (b) The system would need a microprocessor that compares the readings against a threshold and automatically triggers an actuator (for example, closing a weatherproof cover) without waiting for a human decision [2].

7. (a) Two-point calibration checks the sensor at both the low and high ends of its working range and adjusts for offset and scale error, which corrects a sensor that has drifted consistently out of true across its range, whereas one-point calibration only checks against a single reference value and cannot correct for a scale error [2]. (b) Multipoint calibration would be needed where the sensor’s response is not perfectly linear across its range, so checking only two points would not reveal or correct inaccuracies that occur at points in between [2].

8. (a) An infrared sensor detects the heat given off by a human body, allowing it to detect an intruder’s presence without requiring any physical contact or the intruder triggering a switch directly [2]. (b) Using two sensor types together reduces false triggers, since an event that only one sensor type might misinterpret (for example, a sound sensor picking up an unrelated noise) is less likely to also trigger a second, independent sensor type unless an actual intruder is present [2].

9. (a) A temperature sensor takes a reading of the room temperature [1]; a microprocessor compares this reading against a stored threshold (the set point) [1]; if the reading is below the threshold, the microprocessor sends a signal to an actuator that switches the boiler on [1]. (b) The system must be a closed loop because room temperature changes continuously, so the sensor must keep being re-checked and the boiler switched on or off repeatedly as conditions change [1]. A system that only checked the temperature once would switch the boiler on or off a single time and then never respond again, even if the room later became too hot or too cold [1].

10. (a) Sensor: the light sensor detects a vehicle blocking the beam at the barrier. Decision box: is a vehicle present? If yes, proceed; if no, continue checking. Actuator: if a vehicle is detected (and any other condition, such as payment, is met), the motorised actuator raises the barrier arm; once the vehicle has passed, the barrier is lowered again [3]. (b) Representing control processing as an algorithm or flowchart makes the decision-making logic explicit and checkable, and links the sensor reading, the threshold comparison, and the actuator’s response into a single, precise sequence that could be implemented in a real control program [1].

A note on exam technique for this topic

The most common way marks are lost on this topic is blurring the line between monitoring and control in a described scenario, so before answering any question, check whether the system merely records a value for a human to review or automatically triggers a response — the two are tested as a deliberate contrast, not interchangeable terms. When asked to link a sensor to a real device, always state the specific property the sensor measures and why that property matches the scenario’s need, rather than naming the sensor alone. For flowchart-style questions, make sure your answer shows all three elements the mark scheme expects: the sensor reading, a decision box comparing it to a threshold, and the actuator action as the outcome — and remember that a genuine control system re-checks the sensor continuously rather than acting once and stopping.