← IGCSE Computer Science Paper 1

Describing how an automated system works

Describe the system: the sensor measures, the microprocessor compares the reading with a stored value, the actuator responds, and the process repeats.

Part of: IGCSE Computer Science 0478 — 6.1 Automated Systems — Module 27, QCE Digital Solutions Unit 3 — Interactions Between Users, Data and Digital Systems — Module 88

Understanding Describing how an automated system works in IGCSE Computer Science Paper 1

What it does: This names the actuator and shows it responding after the comparison. Saying the process repeats shows the system keeps monitoring and responding, which marks a full answer. A full answer names the sensor, what it measures, the microprocessor comparing with a stored value, and the actuator that responds. The wrong answer misses all of these. Automated systems repeat the cycle of measure, compare and respond. This is often called a loop, and it is worth a mark in an exam. Saying the sensor makes the decision is the most common mistake, because the sensor has no processing ability.

Common mistakes: The sensor only measures. The microprocessor does the comparing, so line 2 should be 'Microprocessor compares it'. The actuator only responds, for example by switching on the lamp. The microprocessor compares the reading, so line 2 should be 'Microprocessor compares it'.

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This module's key terms are also in a printable crossword (Modules 580–607) and word search (Modules 553–607).

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Learning
Duo
Which answer gives the full four-part description of an automated greenhouse heater?
The greenhouse gets cold so the heater turns on and warms the plants up.The temperature sensor measures the air, the microprocessor compares the reading with the stored value, and the heater (actuator) switches on or off.
Matches
The sensor decides to turn on the heater.
↓
Sensors only measure and send data. The microprocessor makes the decision by comparing the reading with the stored value.
Applying
Meanings
Term
sensor, microprocessor, stored value, actuator
Meaning
Describe the system: the sensor measures, the microprocessor compares the reading with a stored value, the actuator responds, and the process repeats.
Practice
storedValue ← 20
Testing
Gaps
The measures the temperature.
Check Answer
Spots
1Sensor measures temperature
2Sensor compares it

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Quick Questions

1. Which answer gives the full four-part description of an automated greenhouse heater?
A. The temperature sensor measures the air, the microprocessor compares the reading with the stored value, and the heater (actuator) switches on or off. ✓
B. The greenhouse gets cold so the heater turns on and warms the plants up.
A full answer names the sensor, what it measures, the microprocessor comparing with a stored value, and the actuator that responds. The wrong answer misses all of these.
2. Who compares the sensor reading with the stored value?
A. The microprocessor ✓
B. The sensor
The sensor only measures and sends data. The microprocessor makes the decision by comparing the reading with the stored value.
3. Which sentence shows the common mistake?
A. The sensor decides to turn the fan on. ✓
B. The microprocessor decides to turn the fan on.
Sensors do not make decisions. They only capture data. The microprocessor decides and then tells the actuator what to do.
4. Which part of the answer is needed to explain what the microprocessor does?
A. It measures the temperature of the room.
B. It compares the reading with a stored value. ✓
Measuring is the job of the sensor. The microprocessor compares the reading with a stored value.
5. In a street light system, which is the actuator?
A. The light sensor that detects darkness
B. The lamp that switches on ✓
The actuator is the output device that responds. The light sensor is the input that measures the light level.

Match the Pairs

The temperature sensor measures the room temperature. → Step 1 of the answer: name the sensor and say what it measures.
The microprocessor compares the reading with the stored value. → Step 2 of the answer: the microprocessor makes the decision by comparing the reading with a stored value.
The actuator is the part that responds when the microprocessor decides action is needed. → The microprocessor switches on the actuator, a heater, if the reading is below the stored value.
A complete answer says the process repeats continuously so the system keeps checking. → The sensor keeps measuring and the process repeats.
The sensor decides to turn on the heater. → Sensors only measure and send data. The microprocessor makes the decision by comparing the reading with the stored value.
The microprocessor checks the temperature and the heater turns on. → The answer misses the sensor, the stored value and the actuator, and it does not say the process repeats.

Key Term

sensor, microprocessor, stored value, actuator
Describe the system: the sensor measures, the microprocessor compares the reading with a stored value, the actuator responds, and the process repeats.

Fill in the Blanks

1. The sensor measures the temperature.
Hint: Type the input device that captures data from the surroundings.
2. The sensor only measures. The microprocessor makes the decision.
Hint: Type the part that decides what to do. The sensor does not decide.
3. The microprocessor compares the reading with the stored value in its memory.
Hint: Type the two-word term for the saved number the reading is compared with.
4. If it is too hot, the microprocessor tells the actuator to switch the fan on.
Hint: Type the output device that responds by making something happen.
5. The process repeats so the sensor keeps measuring and the system keeps checking.
Hint: Type the verb that says the cycle happens again and again.

Spot the Error

Question 1
A Sensor measures temperature
B Sensor compares it
C with the stored value
D Actuator turns the heater on
E The process repeats
Line B — The sensor only measures. The microprocessor does the comparing, so line 2 should be 'Microprocessor compares it'.
Question 2
A Sensor measures brightness
B Actuator compares it
C with the stored value
D Actuator switches the lamp on
Line B — The actuator only responds, for example by switching on the lamp. The microprocessor compares the reading, so line 2 should be 'Microprocessor compares it'.
Question 3
A Sensor measures soil moisture
B Microprocessor opens the valve
C with the stored value
D Actuator opens the valve
Line B — The microprocessor compares and decides, but it is the actuator that opens the valve. Line 2 should be 'Microprocessor compares it'.
Question 4
A Actuator measures air pressure
B Microprocessor compares it
C with the stored value
D Actuator opens the vent
Line A — Measuring is the job of the sensor, not the actuator. Line 1 should be 'Sensor measures air pressure'.
Question 5
A Microprocessor measures speed
B Microprocessor compares it
C with the stored value
D Actuator applies the brakes
E The process repeats
Line A — The microprocessor does not measure anything. The sensor measures the speed and sends the reading on, so line 1 should be 'Sensor measures speed'.

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