← IGCSE Computer Science Paper 1

Flow sensor

An input device that measures how much liquid or gas moves past a point in a set time (the flow rate). Used in water meters, fuel systems, pipelines and irrigation.

Part of: IGCSE Computer Science 0478 — 3.2 Input and Output Devices — Module 36, IGCSE Computer Science 0478 — 6.1 Automated Systems — Module 16

Understanding Flow sensor in IGCSE Computer Science Paper 1

What it does: The flow sensor detects water moving through the pipe, and the system adds that flow to the running total used for billing. A flow sensor captures the flow rate. Temperature would need a temperature sensor. Sensors capture data from the environment and send it to a processor. They are input devices. A drop in flow rate could show a leak or blockage. Humidity is the amount of water vapour in the air. A flow sensor measures how much liquid or gas moves past a point in a given time.

Common mistakes: The water meter should output the total volume used (litres), not the flow rate. Line 4 should be OUTPUT litres. The irrigation loop should run until the total water reaches 100. With <= the loop would stop straight away. It should be UNTIL total >= 100.

Class: _____________________  ·  Name: _____________________  ·  Date: _________

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This module's key terms are also in a printable crossword (Modules 273–282) and word search (Modules 262–282).

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Learning
Duo
What does a flow sensor measure?
How much liquid or gas moves past a point in a given timeHow hot the liquid or gas is
Matches
A flow sensor measures the temperature of a liquid in a pipe
↓
A flow sensor measures how much liquid or gas moves past a point in a set time, not its temperature. A temperature sensor measures temperature.
Applying
Meanings
Term
flow sensor
Meaning
An input device that measures how much liquid or gas moves past a point in a set time (the flow rate). Used in water meters, fuel systems, pipelines and irrigation.
Practice
flowRate ← READ_FLOW_SENSOR()
Testing
Gaps
flowRate
Check Answer
Spots
3litres ← flowRate * minutes
4OUTPUT flowRate

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Quick Questions

1. What does a flow sensor measure?
A. How much liquid or gas moves past a point in a given time ✓
B. How hot the liquid or gas is
A flow sensor captures the flow rate. Temperature would need a temperature sensor.
2. Which data does a flow sensor capture?
A. Flow rate, such as litres per minute ✓
B. Brightness of light in a room
Flow rate is the amount of liquid or gas passing a point in a set time. Brightness is measured by a light sensor.
3. Which system is most likely to use a flow sensor?
A. A burglar alarm that detects someone walking into a room
B. A water meter measuring how much water a house uses ✓
Water meters count how much water flows through a pipe. Burglar alarms use infra-red or proximity sensors to detect movement.
4. A farmer wants to know how much water an irrigation system delivers to a field. Which sensor should be used?
A. Flow sensor ✓
B. Magnetic field sensor
A flow sensor in the irrigation pipe measures how much water passes through, so the farmer can control watering.
5. Is a flow sensor an input device or an output device?
A. Output device, because it shows the flow on a screen
B. Input device, because it sends data to the processor ✓
Sensors capture data from the environment and send it to a processor. They are input devices.

Match the Pairs

flow sensor → An input device that measures how much liquid or gas moves past a point in a set time
flow rate → The data a flow sensor captures: the volume of liquid or gas passing a point each second or minute
A water meter uses a flow sensor to record how much water a household uses → IF flow_sensor > 0 THEN add_to_total
An irrigation system uses a flow sensor to check that enough water reaches the crops → IF flow_rate < 10 THEN sound_alarm
A flow sensor measures the temperature of a liquid in a pipe → A flow sensor measures how much liquid or gas moves past a point in a set time, not its temperature. A temperature sensor measures temperature.
A flow sensor is an output device that pumps fuel through a pipeline → A flow sensor is an input device that measures flow. It does not move the fuel. A pump or valve is an actuator that controls the flow.

Key Term

flow sensor
An input device that measures how much liquid or gas moves past a point in a set time (the flow rate). Used in water meters, fuel systems, pipelines and irrigation.

Fill in the Blanks

1. // Flow sensor in a water meter INPUT flowRate
Hint: Type the keyword that reads data into the program from an input device such as the flow sensor.
2. IF flowRate < 5 THEN OUTPUT "Low flow in pipeline" ENDIF
Hint: Type the comparison operator that checks whether the flow rate is less than the limit.
3. litresUsed ← flowRate * minutes
Hint: Type the operator that multiplies the flow rate by the time to find the total volume.
4. IF flowRate > 20 THEN OUTPUT "Close irrigation valve" ENDIF
Hint: Type the keyword that closes the selection block started by IF.
5. OUTPUT "Fuel used: ", litresUsed
Hint: Type the keyword that sends information from the program to an output device such as a screen.

Spot the Error

Question 1
A flowRate ← 12
B minutes ← 5
C litres ← flowRate * minutes
D OUTPUT flowRate
Line D — The water meter should output the total volume used (litres), not the flow rate. Line 4 should be OUTPUT litres.
Question 2
A total ← 0
B REPEAT
C total ← total + READ(flow)
D UNTIL total <= 100
E OUTPUT "Close valve"
Line D — The irrigation loop should run until the total water reaches 100. With <= the loop would stop straight away. It should be UNTIL total >= 100.
Question 3
A flow ← READ(fuelFlow)
B IF flow = 0
C OUTPUT "No fuel moving"
D ENDIF
Line B — An IF statement needs THEN at the end of the condition. It should be IF flow = 0 THEN.
Question 4
A inFlow ← READ(sensorA)
B outFlow ← READ(sensorB)
C IF inFlow < outFlow THEN
D OUTPUT "Possible leak"
E ENDIF
Line C — A pipeline leak is suspected when more liquid flows in than flows out. The comparison is reversed. It should be IF inFlow > outFlow THEN.
Question 5
A WHILE tankFilling = TRUE
B flow ← READ(levelSensor)
C total ← total + flow
D ENDWHILE
Line B — A level sensor measures how high the liquid is, not how much moves past a point. To get flow data you must read the flow sensor: READ(flowSensor).

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