MECHATRONICS UPDATED PRACTICE TEST QUESTIONS
AND SOLUTIONS RATED A+
✔✔Capacitive sensor - ✔✔1-5mm, non contact, expensive, external object alter the
capacitance of internal capacitor, detect non metallic object in human body, fill level for
bottle, user input in smartphone, proximity sensing
✔✔Inductive sensor - ✔✔1-5mm, non contact, expensive, requires metal object, detect
change in inductance, sensing proximity of metal object, measuring speed of spur gear
✔✔Linear resistive sensor - ✔✔<50cm, contact, cheap to expensive, short range linear
position, change resistance with distance
✔✔Ultrasonic sensor - ✔✔1cm-10m, non contact, expensive, tank level sensing,
parking sensor, presence of item of conveyor belt, hand held distance measuring device
✔✔Optical distance sensor (laser diode) - ✔✔few cm - several km, non contact,
expensive, light emitter and receiver, measure time or amount reflected back, automatic
door opening/closing, speed measurement, surveying, mapping
✔✔Linear variable differential transformer (LVDT) - ✔✔1-50cm, contact ,expensive,
accurate distance measurement over short range
✔✔wire reel extender - ✔✔1-50m, contact, medium, measure telescopic crane arm
extension, fork height on fork-lift truck
✔✔Global positioning system (GPS) - ✔✔location anywhere, accuracy =<10m and
differential <5cm, cheap receiver, air/sea/ground vehicle position, surveying system,
assets tracking
✔✔Optical encoder - ✔✔360 degree contentious, accuracy: within 1 bit, contact, cheap
to expensive, absolute or relative shaft position, measure shaft speed, position, control
of servo motor, input sensor of human control
✔✔variable resistor - ✔✔340 degree, accuracy: infinite, contact, cheap to expensive,
change in resistance with angle, measure shaft speed, shaft position, control of
servomotor, input sensor for human control
✔✔Measure velocity via DC generator - ✔✔speed limit of generator and wheel radius,
contact, voltage generate proportional to speed, vehicle speed, measuring speed of
machinery
✔✔MEMS Gyroscope - ✔✔up to 20,000 degree/sec, non contact, vehicle control,
stabilisation, autonomous system, inertial sensing of orientation
, ✔✔MEMS - ✔✔micro electro-mechanical system
✔✔MEMS accelerometer - ✔✔up to 10,000g, non contact, vehicle control, stabilisation,
autonomous system, inertial sensing of orientation, vibration measurement, model
analysis of structures
✔✔force load cell - linear - ✔✔mN to MN, accuracy: <0.01%, response time: fast, cheap
to expensive, load monitoring of structure and machines, weighing work calculations
✔✔Angular load cell - ✔✔mNm to kNm, accuracy: <0.01%, response time: fast, cheap
to expensive, load monitoring of rotating shafts
✔✔Turbine (sensor) - ✔✔any size, accuracy 1-10%, response time: depends on inertia
of turbine and scale, cheap, contact, speed proportional to flow velocity, use for general
purpose flow sensing, weather/wind measurement
✔✔Ultrasonic (pressure) sensor - ✔✔up to 3000l/s, accuracy: 1%, response time: fast,
expensive, non contact, measure change in speed through different medium or time it
takes, petrochemical, food industries, water and sewage metering
✔✔Optical sensor - ✔✔up to 3000l/s, accuracy: 1%, response time: fast, very
expensive, non contact, specialist applications, transparent fluids or gases in
petrochemical industry
✔✔Pressure differential - ✔✔scalable, accuracy: 1%, response time: fast, moderate
price, contact, use bernoulii equation, general purpose gas and liquid, water,
petrochemicals industrial application
✔✔Thermistor (Thermal resistor, RTD) - ✔✔73-1123K, Typical accuracy: 0.001 - 0.1
degree F, Response time: moderate, contact, cheap,general purpose temperature
sensing that doesn't require a fast response, especially for applications that require long
term stability, fridges and
chiller cabinet monitoring, medical applications
✔✔Thermocouple - ✔✔80-2094k, accuracy: within 10m, response time: fast, moderate
cost, contact, application where fast response time is required, pyrometry
✔✔Attenuator - ✔✔gain <1
✔✔Amplifier - ✔✔gain >1
✔✔Rectifier - ✔✔output voltage >=0 regardless whether the input voltage is positive or
negative
AND SOLUTIONS RATED A+
✔✔Capacitive sensor - ✔✔1-5mm, non contact, expensive, external object alter the
capacitance of internal capacitor, detect non metallic object in human body, fill level for
bottle, user input in smartphone, proximity sensing
✔✔Inductive sensor - ✔✔1-5mm, non contact, expensive, requires metal object, detect
change in inductance, sensing proximity of metal object, measuring speed of spur gear
✔✔Linear resistive sensor - ✔✔<50cm, contact, cheap to expensive, short range linear
position, change resistance with distance
✔✔Ultrasonic sensor - ✔✔1cm-10m, non contact, expensive, tank level sensing,
parking sensor, presence of item of conveyor belt, hand held distance measuring device
✔✔Optical distance sensor (laser diode) - ✔✔few cm - several km, non contact,
expensive, light emitter and receiver, measure time or amount reflected back, automatic
door opening/closing, speed measurement, surveying, mapping
✔✔Linear variable differential transformer (LVDT) - ✔✔1-50cm, contact ,expensive,
accurate distance measurement over short range
✔✔wire reel extender - ✔✔1-50m, contact, medium, measure telescopic crane arm
extension, fork height on fork-lift truck
✔✔Global positioning system (GPS) - ✔✔location anywhere, accuracy =<10m and
differential <5cm, cheap receiver, air/sea/ground vehicle position, surveying system,
assets tracking
✔✔Optical encoder - ✔✔360 degree contentious, accuracy: within 1 bit, contact, cheap
to expensive, absolute or relative shaft position, measure shaft speed, position, control
of servo motor, input sensor of human control
✔✔variable resistor - ✔✔340 degree, accuracy: infinite, contact, cheap to expensive,
change in resistance with angle, measure shaft speed, shaft position, control of
servomotor, input sensor for human control
✔✔Measure velocity via DC generator - ✔✔speed limit of generator and wheel radius,
contact, voltage generate proportional to speed, vehicle speed, measuring speed of
machinery
✔✔MEMS Gyroscope - ✔✔up to 20,000 degree/sec, non contact, vehicle control,
stabilisation, autonomous system, inertial sensing of orientation
, ✔✔MEMS - ✔✔micro electro-mechanical system
✔✔MEMS accelerometer - ✔✔up to 10,000g, non contact, vehicle control, stabilisation,
autonomous system, inertial sensing of orientation, vibration measurement, model
analysis of structures
✔✔force load cell - linear - ✔✔mN to MN, accuracy: <0.01%, response time: fast, cheap
to expensive, load monitoring of structure and machines, weighing work calculations
✔✔Angular load cell - ✔✔mNm to kNm, accuracy: <0.01%, response time: fast, cheap
to expensive, load monitoring of rotating shafts
✔✔Turbine (sensor) - ✔✔any size, accuracy 1-10%, response time: depends on inertia
of turbine and scale, cheap, contact, speed proportional to flow velocity, use for general
purpose flow sensing, weather/wind measurement
✔✔Ultrasonic (pressure) sensor - ✔✔up to 3000l/s, accuracy: 1%, response time: fast,
expensive, non contact, measure change in speed through different medium or time it
takes, petrochemical, food industries, water and sewage metering
✔✔Optical sensor - ✔✔up to 3000l/s, accuracy: 1%, response time: fast, very
expensive, non contact, specialist applications, transparent fluids or gases in
petrochemical industry
✔✔Pressure differential - ✔✔scalable, accuracy: 1%, response time: fast, moderate
price, contact, use bernoulii equation, general purpose gas and liquid, water,
petrochemicals industrial application
✔✔Thermistor (Thermal resistor, RTD) - ✔✔73-1123K, Typical accuracy: 0.001 - 0.1
degree F, Response time: moderate, contact, cheap,general purpose temperature
sensing that doesn't require a fast response, especially for applications that require long
term stability, fridges and
chiller cabinet monitoring, medical applications
✔✔Thermocouple - ✔✔80-2094k, accuracy: within 10m, response time: fast, moderate
cost, contact, application where fast response time is required, pyrometry
✔✔Attenuator - ✔✔gain <1
✔✔Amplifier - ✔✔gain >1
✔✔Rectifier - ✔✔output voltage >=0 regardless whether the input voltage is positive or
negative
