Flashcards · 9626 · AS Topic 3

Monitoring and control (AS Level) flashcards

8 cards on AS Topic 3, subtopics 3.1 to 3.2. Pick a subtopic or study them all.

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Monitoring vs control: Monitoring reads and records values for a person to review, e.g. a weather station logging humidity. Control triggers an automatic response with no human decision, e.g. a greenhouse vent opening at a set temperature.
Name eight sensors on the 9626 syllabus: Any eight of: light/UV, temperature, pressure, humidity, pH, gas (oxygen, CO₂, CO, nitrogen oxides), sound, infrared, touch, (electro)magnetic field, proximity.
One-point vs two-point vs multipoint calibration: One-point: checks against one known reference value. Two-point: checks at a low and a high point, correcting offset and scale error. Multipoint: checks several points, for the highest accuracy when the response is not linear.
Why must a working sensor still be calibrated?: It may respond to changes but give every reading shifted by a consistent offset. Only comparing it with a known reference corrects this systematic error; repeated readings do not.

Describe the sensor-microprocessor-actuator loop in a greenhouse vent system: A temperature sensor takes a reading; the microprocessor compares it with a stored threshold; if it is higher, an actuator opens the vent; the sensor is checked continuously and the vent closes when the temperature falls.
Name six types of actuator on the 9626 syllabus: Any six of: linear, rotary, soft, hydraulic, pneumatic, electric, thermal, magnetic, mechanical.
Which sensor would detect an intruder's body heat in a burglar alarm, and which a phone held to the ear?: Body heat: an infrared sensor (no contact needed). Phone near the ear: a proximity sensor.
Why is a control system called a closed loop?: After acting, it keeps re-checking the sensor, so the output affects the next input. It does not act once and stop.