AME Unit 9 Probes, Thermistors, Sensors Quiz

Correct Answer:

A. Change in Electrical Resistance: The PT100 probe measures temperature based on the principle that the electrical resistance of platinum increases with temperature. The probe’s resistance is measured and converted into a temperature reading.

Explanation:

• A. Correct: PT100 probes operate on the principle that the electrical resistance of platinum increases in a known, linear relationship with temperature. This change in resistance is measured and converted to a temperature reading, making it an accurate and reliable temperature measurement device.
• B. Incorrect: The thermoelectric effect is used in thermocouples, not PT100 probes. It involves generating a voltage from the junction of two different metals subjected to a temperature difference.
• C. Incorrect: Capacitance variation is not used in PT100 probes. This principle is more relevant to other types of sensors that measure temperature through changes in capacitance.
• D. Incorrect: Optical emission is not applicable to PT100 probes. This principle is used in methods like pyrometry, which measure temperature based on the radiation emitted by an object.

Correct Answer:

A. Platinum and 100 Ohms at 0°C: The "PT" stands for platinum, and "100" indicates that the probe has a resistance of 100 ohms at 0°C.

Explanation:

• A. Correct: The PT100 probe is named for its use of platinum ("PT") and its resistance of 100 ohms at 0°C. This naming convention helps identify the specific type of resistance thermometer and its base resistance value.
• B. Incorrect: The "100" does not refer to the measurement range of the probe, but rather to its resistance value at 0°C.
• C. Incorrect: The "100" in PT100 does not refer to the number of wire turns in the sensing element; it refers to the resistance value at 0°C.
• D. Incorrect: The "100" does not indicate the length of the sensing element but rather the resistance at 0°C. The probe length is not specified by this designation.

Correct Answer:

A. Platinum Wire Wrapped Around a Ceramic Core: The sensing element consists of a thin platinum wire wound around a ceramic core. The resistance of the platinum wire changes with temperature, and this change is used to measure temperature.

Explanation:

• A. Correct: The PT100 probe uses a sensing element made of a thin platinum wire wound around a ceramic core. Platinum is chosen for its stable and predictable change in resistance with temperature, providing accurate temperature measurements.
• B. Incorrect: Copper wire is not used in PT100 probes. While copper wire does change resistance with temperature, it does not have the stability and precision required for PT100 sensors.
• C. Incorrect: This describes a thermocouple, not a PT100 probe. Thermocouples use two different metals to create a voltage based on temperature differences.
• D. Incorrect: While resistance film on a substrate can be used in some temperature sensors, it is not the typical construction for PT100 probes. PT100 sensors rely on platinum wire for its accuracy and stability.

Correct Answer:

A. Two Dissimilar Metals Produce a Voltage: A thermocouple operates by generating a voltage when two dissimilar metals are joined together and exposed to different temperatures, with the voltage being proportional to the temperature difference.

Explanation:

• A. Correct: A thermocouple consists of two different metals joined at one end. When this junction is exposed to different temperatures, it produces a voltage that can be measured. The voltage generated is directly related to the temperature difference between the junctions, allowing for temperature measurement.
• B. Incorrect: A thermocouple does not operate based on the expansion of a single metal but on the voltage produced by the junction of two dissimilar metals.
• C. Incorrect: Changes in electrical resistance are not the basis of thermocouple operation; that principle is more relevant to resistance temperature detectors (RTDs).
• D. Incorrect: Thermocouples do not operate based on magnetic fields; they generate voltage from the temperature difference at the junction of two dissimilar metals.

Correct Answer:

A. Limited Accuracy; Use of Calibration: Thermocouples have limited accuracy compared to other temperature sensors, but this is overcome by regularly calibrating the thermocouple to ensure accurate measurements.

Explanation:

• A. Correct: Thermocouples can be less accurate than other temperature sensors. To overcome this limitation, they are regularly calibrated against known temperature standards to maintain accuracy.
• B. Incorrect: Thermocouples generally have a good response time for most applications. Insulation is not typically used to address response time but to protect the thermocouple or manage heat transfer in specific conditions.
• C. Incorrect: While electromagnetic interference can affect some temperature sensors, it is less of an issue with thermocouples when proper wiring practices are followed. Shielded cables are more commonly used for other types of sensors that are more sensitive to interference.
• D. Incorrect: Thermocouples are available in different types, with varying temperature ranges, to cover a wide range of applications. The use of special alloys is a solution for extending the temperature range, but this is not the primary limitation addressed.

Correct Answer:

A. Radar Level Sensors, Ultrasonic Sensors, Capacitance Sensors, Float Switches, Laser Level Sensors

Explanation:

• A. Correct:
  • Radar Level Sensors: Use radio waves to detect the level of the fuel in the tank.
  • Ultrasonic Sensors: Use ultrasonic waves to measure the distance to the surface of the fuel.
  • Capacitance Sensors: Measure changes in capacitance caused by the fuel level.
  • Float Switches: Use a float that moves with the fuel level and activates switches to indicate levels.
  • Laser Level Sensors: Use laser beams to measure the distance to the fuel surface.
• B. Incorrect:
  • Thermocouples, Strain Gauges, Pressure Transducers, Vibration Sensors, Fiber Optic Sensors: While some of these sensors are used in various industrial applications, they are not typically used for remote level monitoring of fuel oil tanks.
• C. Incorrect:
  • Thermometers, pH Meters, Magnetic Field Sensors, Humidity Sensors, Sound Level Meters: These instruments are used for different types of measurements and are not suitable for level monitoring of fuel tanks.
• D. Incorrect:
  • Speed Sensors, Proximity Sensors, Displacement Sensors, Optical Sensors, Gas Detectors: These sensors are used in various applications but do not generally serve the purpose of remotely monitoring fuel oil levels.

Correct Answer:

A. The bi-metallic strip bends in response to temperature changes, and this bending movement operates a mechanical pointer or switch to indicate the temperature.

Explanation:

• A. Correct: Bi-metallic strips consist of two different metals bonded together. When the temperature changes, the metals expand or contract at different rates, causing the strip to bend. This bending can move a mechanical pointer or operate a switch, providing a direct temperature indication.
• B. Incorrect: Bi-metallic strips do not generate an electrical signal. They rely on mechanical bending to measure temperature, rather than producing an electrical output.
• C. Incorrect: Bi-metallic strips do not change color with temperature. They function based on physical bending rather than color change.
• D. Incorrect: Bi-metallic strips do not measure temperature by changing thermal conductivity. They use mechanical deformation due to different thermal expansion rates of the metals involved.

Correct Answer:

A. They have limited accuracy and resolution compared to electronic temperature sensors.

Explanation:

• A. Correct: Bi-metallic strips generally have lower accuracy and resolution compared to electronic sensors like thermocouples or RTDs. They are better suited for applications where high precision is not critical.
• B. Incorrect: Bi-metallic strips are sensitive to temperature changes, but they can have a slower response time compared to some electronic sensors. The issue is more about accuracy rather than sensitivity or response time.
• C. Incorrect: Bi-metallic strips are not typically affected by electromagnetic interference, as they operate on mechanical bending rather than electronic signals.
• D. Incorrect: Bi-metallic strips generally do not require frequent calibration. They are mechanical devices that maintain their calibration unless physically damaged or altered.

Correct Answer:

A. Temperature gauges and thermostats

Explanation:

• A. Correct: Bi-metallic strips are commonly used in temperature gauges and thermostats. They are designed to bend with temperature changes, making them suitable for mechanical temperature measurement and control.
• B. Incorrect: Bi-metallic strips are not typically used in pressure sensors. Pressure sensors generally use different technologies like strain gauges or piezoelectric materials.
• C. Incorrect: Bi-metallic strips are not used in flow meters. Flow meters typically use methods such as electromagnetic, ultrasonic, or turbine principles.
• D. Incorrect: Bi-metallic strips are not used as vibration dampers. Vibration damping is usually handled by materials or devices specifically designed for that purpose, such as rubber mounts or damping pads.

Correct Answer:

B. A potentiometer varies resistance within a circuit by adjusting a sliding contact along a resistive track, allowing it to control voltage and current flow.

Explanation:

• B. Correct: A potentiometer operates by varying the resistance in a circuit through a sliding or rotating contact along a resistive element. This adjustment changes the voltage and current flow in the circuit, making it useful for controlling and calibrating electrical signals.
• A. Incorrect: This describes a voltmeter or digital voltmeter rather than a potentiometer. A potentiometer does not provide a direct digital readout of voltage.
• C. Incorrect: This describes a principle more similar to an analog meter or electrical transducer, not a potentiometer. A potentiometer’s primary function is to adjust resistance, not to convert mechanical movement into an electrical signal.
• D. Incorrect: This describes the operation of a temperature sensor or thermistor, not a potentiometer. Potentiometers are not used to measure temperature directly; they adjust resistance to control electrical parameters.

Correct Answer:

B. By converting rotational movement into a variable resistance through a rotating wiper that contacts a resistive element, which then provides a corresponding voltage output.

Explanation:

• B. Correct: A potentiometer measures rotary movement by having a rotating wiper (contact) that moves along a circular resistive track. As the wiper rotates, it changes the resistance in the circuit. The corresponding voltage output from the potentiometer varies with the angle of rotation, allowing measurement of rotary movement.
• A. Incorrect: A linear resistive track is used for linear movement measurements, not rotary. Potentiometers for rotary movement have a circular resistive track.
• C. Incorrect: This describes a capacitive position sensor, not a potentiometer. A potentiometer does not measure rotary movement by changes in capacitance.
• D. Incorrect: This describes a type of rotary position sensor or analog meter, not a potentiometer. Potentiometers do not use magnetic fields for measuring rotary movement.

Correct Answer:

B. To detect and measure temperature changes in various systems.

Explanation:

• B. Correct: Thermistors are widely used on vessels to measure and monitor temperature changes in various systems, such as engine cooling systems, fuel tanks, and environmental monitoring.
• A. Incorrect: Thermistors do not measure the concentration of dissolved gases. This task is typically performed by gas sensors.
• C. Incorrect: Thermistors do not measure pH levels. pH sensors or probes are used for this purpose.
• D. Incorrect: Thermistors are not used to measure the speed of the vessel. Speed measurement is typically done using speed logs or other specialized instruments.

Correct Answer:

C. Ceramic materials and metal oxides.

Explanation:

• C. Correct: Thermistors are commonly constructed from ceramic materials and metal oxides. These materials have properties that change significantly with temperature, allowing thermistors to accurately measure temperature variations.
• A. Incorrect: Silicon and gallium arsenide are used in semiconductor devices, not typically in thermistors.
• B. Incorrect: Iron and cobalt are not standard materials for thermistor construction; they are more commonly used in magnetic and structural applications.
• D. Incorrect: Aluminum and copper are metals used in various electrical applications but are not typical materials for thermistor construction.

Correct Answer:

C. Thermistors operate by changing their electrical resistance in response to temperature changes.

Explanation:

• C. Correct: The principle of operation of a thermistor is based on its electrical resistance changing with temperature. The resistance of a thermistor decreases or increases depending on whether it is a Negative Temperature Coefficient (NTC) or Positive Temperature Coefficient (PTC) thermistor.
• A. Incorrect: Changes in capacitance are not the principle of operation for thermistors. This principle applies to other types of temperature sensors.
• B. Incorrect: Magnetic field strength is not used in the operation of thermistors. This principle might apply to other types of sensors, like magnetic field sensors.
• D. Incorrect: Changes in light absorption are not related to thermistors. This principle is more related to optical temperature sensors or photodetectors.

Correct Answer:

A. A Bourdon tube cannot be used to measure temperature as it is specifically designed for pressure measurement.

Explanation:

• A. Correct: A Bourdon tube is specifically designed for measuring pressure. It operates by detecting changes in pressure that cause mechanical movement of the tube, which is not suitable for measuring temperature.
• B. Incorrect: Filling a Bourdon tube with a temperature-sensitive liquid is not a standard method for measuring temperature. This approach does not apply to the operation of a Bourdon tube.
• C. Incorrect: A Bourdon tube does not connect to a temperature sensor for measuring temperature. It is designed for pressure measurement and does not integrate with temperature sensors in this way.
• D. Incorrect: A Bourdon tube operates based on pressure changes, not temperature. It does not convert temperature changes into mechanical movement directly.

Correct Answer:

A. A Bourdon tube can be used to measure the temperature of the engine room exhaust gases, typically located near the exhaust manifold.

Explanation:

• A. Correct: Although Bourdon tubes are primarily used for pressure measurement, in some specific applications, they might be used in conjunction with other systems to measure temperature, such as monitoring exhaust gases where accurate pressure and temperature data are crucial.
• B. Incorrect: The measurement of fuel oil temperature would typically be done with a thermometer designed for liquids, not a Bourdon tube.
• C. Incorrect: Temperature measurements of seawater intake are generally performed with temperature sensors or probes designed for such conditions, not with a Bourdon tube.
• D. Incorrect: Measuring the temperature of boiler water typically requires temperature sensors designed for high-temperature environments, rather than a Bourdon tube.

Correct Answer:

B. A pressure-sensing instrument that uses a curved metal tube which straightens as pressure increases, with the resulting movement used to indicate pressure on a dial.

Explanation:

• B. Correct: A Bourdon tube is a mechanical pressure measurement device. It consists of a curved metal tube that tends to straighten out when pressure is applied. This movement is then translated into a dial reading, providing the pressure measurement.
• A. Incorrect: This describes a temperature-sensitive device, not a Bourdon tube. Temperature measurement is not the function of a Bourdon tube.
• C. Incorrect: This describes a flow meter, not a Bourdon tube. Bourdon tubes are used for measuring pressure, not flow.
• D. Incorrect: This describes a temperature sensor based on electrical resistance changes, not a Bourdon tube. A Bourdon tube measures pressure through mechanical movement.

Correct Answer:

A. Using a thermocouple connected to a remote display unit.

Explanation:

• A. Correct: Thermocouples are widely used for remote temperature measurement, where the temperature is measured at one location and the data is transmitted to a remote display unit.
• B. Incorrect: Bourdon tubes are primarily used for pressure measurement, not typically for remote temperature measurement.
• C. Incorrect: Bimetallic strips are used in temperature measurement, but they typically provide local readings, not remote measurements.
• D. Incorrect: A mercury-in-glass thermometer is a direct-reading instrument and cannot be used for remote measurement.

Correct Answer:

C. Using an electromagnetic flow meter with a digital output to a control panel.

Explanation:

• A. Incorrect: An orifice plate with a local differential pressure gauge can measure flow rate, but it does not provide a remote measurement.
• B. Incorrect: A rotameter typically provides a local indication of flow rate and does not transmit data remotely.
• C. Correct: An electromagnetic flow meter can accurately measure flow rate and transmit this data digitally to a remote control panel, making it suitable for remote monitoring.
• D. Incorrect: A Venturi meter can measure flow rate, but when paired with a mechanical dial, it is more suited for local measurement rather than remote measurement.

Correct Answer:

B. The rotation of the impeller generates pulses, which are counted by a microcontroller and then converted into a digital readout of flow rate in litres per minute.

Explanation:

• A. Incorrect: While some flowmeters might use magnetic sensors, the generation of a magnetic field by the impeller itself does not directly convert into a digital readout without electronic processing.
• B. Correct: In an impeller-type flowmeter, the rotation of the impeller creates pulses as it interrupts or triggers a sensor (often magnetic or optical). These pulses are counted by a microcontroller, which then calculates the flow rate and displays it as a digital value in litres per minute.
• C. Incorrect: An impeller-type flowmeter does not produce a varying resistance; instead, it typically generates pulses related to the flow rate.
• D. Incorrect: While the impeller's rotation is related to the flow rate, the output is not directly digital; it requires processing (such as counting pulses) to convert the rotational speed into a digital flow rate display.

Correct Answer:

B. The impeller rotation generates pulses, which are counted electronically and converted to an analogue voltage proportional to flow rate.

Explanation:

• A. Incorrect: The mechanical movement of an impeller does not directly translate to an analogue dial reading without electronic processing.
• B. Correct: In an impeller-type flowmeter, the rotation of the impeller generates electrical pulses. These pulses are counted over time, and the count is proportional to the flow rate. This count is then electronically processed and converted to an analogue voltage that corresponds to the flow rate in litres per minute.
• C. Incorrect: An impeller-type flowmeter does not work by creating a pressure differential; instead, it relies on the rotational speed of the impeller.
• D. Incorrect: The impeller does not produce significant heat due to friction, and heat is not used as a means of measuring flow rate in this type of flowmeter.

Correct Answer:

B. A floating buoy that rises and falls with the liquid level, activating a switch to send an electrical signal to a control system.

Explanation:

• A. Incorrect: A weighted ball typically does not produce an electrical or digital output signal; it usually provides a direct mechanical action.
• B. Correct: A floating buoy or float switch moves with the liquid level and triggers an electrical switch when it reaches a certain point. This switch sends a signal to a remote control system, which can then adjust the liquid level by controlling pumps or valves.
• C. Incorrect: A submerged probe might measure pressure changes, but it is not a flotation device and does not directly control the liquid level through flotation.
• D. Incorrect: A rotating vane typically measures flow rate rather than liquid level and does not operate based on flotation principles.

Correct Answers:

A. Monitoring fuel tank levels.
C. Detecting the presence of water in the bilge.

Explanation:

• A. Correct: Capacitance probes are commonly used to monitor liquid levels, such as in fuel tanks.
• B. Incorrect: Flow rate measurement typically involves devices like impeller flowmeters or ultrasonic flow sensors, not capacitance probes.
• C. Correct: Capacitance probes can detect the presence of liquids, making them suitable for bilge water detection.
• D. Incorrect: Temperature measurement is typically done using thermocouples or resistance thermometers, not capacitance probes.
• E. Incorrect: Pressure measurement is typically performed with pressure sensors like Bourdon tubes, not capacitance probes.

Correct Answer:

D. They may give inaccurate readings if the liquid has a variable dielectric constant.

Explanation:

• A. Incorrect: While temperature can affect many sensors, capacitance probes are primarily affected by changes in the dielectric constant of the liquid they measure, rather than temperature alone.
• B. Incorrect: Capacitance probes are generally compact and do not require a large amount of space.
• C. Incorrect: Although corrosion is a concern in marine environments, proper material selection and protection usually mitigate this issue for capacitance probes.
• D. Correct: Capacitance probes rely on the dielectric constant of the liquid to measure level accurately. If the dielectric constant varies, it can lead to inaccurate readings.

Correct Answer:

C. By detecting changes in the capacitance between the probe and the tank wall as the liquid level rises or falls, which is then converted into an electrical signal.

Explanation:

• A. Incorrect: Capacitance probes do not generate or use magnetic fields to measure liquid levels.
• B. Incorrect: Capacitance probes measure changes in capacitance, not resistance, to determine liquid levels.
• C. Correct: A capacitance probe works by detecting changes in the capacitance between the probe and the tank wall. As the liquid level changes, the dielectric constant between the probe and the wall changes, altering the capacitance. This change is then converted into an electrical signal that can be used to measure the liquid level.
• D. Incorrect: This describes the operation of an ultrasonic level sensor, not a capacitance probe.

Correct Answer:

B. Ultrasound waves are transmitted towards the fluid surface, and the time it takes for the waves to reflect back to the sensor is used to calculate the fluid level.

Explanation:

• A. Incorrect: Ultrasound waves are used to measure the time it takes for the waves to reflect back from the fluid surface, not to reach the bottom of the tank.
• B. Correct: This method accurately describes how ultrasound level sensors work. The sensor emits ultrasound waves towards the fluid surface, and the time delay of the reflected signal is used to determine the fluid level.
• C. Incorrect: Ultrasound level measurement does not rely on energy absorption by the fluid.
• D. Incorrect: Ultrasound waves are directed towards the fluid surface rather than along the tank walls to measure fluid level.

Correct Answers:

A. Non-contact measurement, reducing the risk of contamination. C. Ability to measure fluid levels in tanks with corrosive or hazardous materials.

Explanation:

• A. Correct: One of the main advantages of ultrasound level measurement is that it is a non-contact method, which means there is no direct contact with the fluid, reducing the risk of contamination.
• B. Incorrect: Ultrasound measurement is generally not highly sensitive to temperature changes, which is not typically considered an advantage.
• C. Correct: Ultrasound is effective in measuring fluid levels in tanks containing corrosive or hazardous materials, as it does not require direct contact with the fluid.
• D. Incorrect: While environmental factors can affect measurements, regular calibration due to such sensitivity is not an advantage but rather a limitation.
• E. Incorrect: Ultrasound can measure fluid levels in a variety of fluids, not just transparent ones.

Correct Answers:

A. Limited effectiveness in tanks with complex internal structures. E. Difficulty in measuring fluid levels in tanks with foam or vapor presence.

Explanation:

• A. Correct: Ultrasound can be less effective in tanks with complex internal structures, such as baffles, which can cause signal reflections and errors.
• B. Incorrect: Ultrasound can measure the level of opaque fluids, so this is not a limitation.
• C. Incorrect: While temperature and pressure can affect accuracy, they are not the primary limitations in most applications.
• D. Incorrect: While ultrasound can be accurate, its performance can vary depending on the fluid density, making this statement incorrect as a limitation.
• E. Correct: The presence of foam or vapor can interfere with the ultrasound signal, making it difficult to obtain accurate measurements.

Explanation:

• A. Correct: This is the correct formula. The strain ($\epsilon$) is calculated by the change in resistance ($\Delta R$) divided by the original resistance ($R$), multiplied by the gauge factor (GF).
• B. Incorrect: This formula is for calculating percentage elongation or strain in terms of length change, not specifically related to strain gauges.
• C. Incorrect: This formula is for calculating stress ($\sigma$), not strain.
• D. Incorrect: This is the formula for calculating the equivalent resistance of two resistors in parallel, not related to strain gauges.

Correct Answers:

A. Monitoring the strain on the ship’s hull to detect structural weaknesses.

C. Monitoring the load on a ship's cargo crane to prevent overloading.

Explanation:

• A. Correct: Strain gauges are used to monitor the strain on a ship's hull, which can help in detecting structural weaknesses or potential failures.
• B. Incorrect: Strain gauges are not used for measuring temperature; thermocouples or resistance temperature detectors (RTDs) would be used for that purpose.
• C. Correct: Strain gauges are commonly used to monitor the load on cargo cranes to ensure that they are not overloaded, which is crucial for safety.
• D. Incorrect: Strain gauges do not measure speed; devices like tachometers are used for this.
• E. Incorrect: Strain gauges do not measure pH levels; specialized sensors are required for pH measurement.

Correct Answer:

B. The strain gauge is connected in a Wheatstone bridge circuit to measure the small changes in resistance accurately, which are then converted into pressure readings.

Explanation:

• A. Incorrect: While voltage changes can be measured, this method is not as precise as using a Wheatstone bridge for small resistance changes.
• B. Correct: The Wheatstone bridge circuit is commonly used with strain gauges because it allows for the precise measurement of very small changes in resistance, which correspond to pressure changes.
• C. Incorrect: A simple voltage divider circuit does not provide the accuracy needed for measuring small changes in resistance due to pressure.
• D. Incorrect: While amplifiers are sometimes used, the key component for accurate measurement is the Wheatstone bridge, which this option does not mention.

Correct Answer:

C. A strain gauge measures strain by detecting changes in electrical resistance as the material to which it is attached is stretched or compressed.

Explanation:

• A. Incorrect: A strain gauge does not operate based on changes in capacitance; it operates based on changes in resistance.
• B. Incorrect: While changes in electrical resistance can be used to measure temperature (as in thermistors), a strain gauge specifically measures mechanical strain, not temperature.
• C. Correct: The primary operation of a strain gauge involves measuring strain through changes in electrical resistance as the material is deformed.
• D. Incorrect: Strain gauges do not measure pressure through magnetic flux; they measure strain through resistance changes.

Correct Answer:

A. Pressure transducer

Explanation:

• A. Correct: A pressure transducer is designed to measure pressure, making it suitable for monitoring lubricating oil pressure remotely.
• B. Incorrect: A thermocouple measures temperature, not pressure.
• C. Incorrect: A flowmeter measures the flow rate of fluids, not pressure.
• D. Incorrect: A strain gauge measures strain, not pressure.
• E. Incorrect: A tachometer measures rotational speed, not pressure.

Correct Answer:

A. Thermocouple

Explanation:

• A. Correct: Thermocouples are widely used for measuring high temperatures, including diesel engine exhaust temperatures, due to their wide temperature range and accuracy.
• B. Incorrect: Pressure gauges measure pressure, not temperature.
• C. Incorrect: Ultrasonic level sensors measure liquid levels, not temperature.
• D. Incorrect: Flowmeters measure the flow rate of liquids or gases, not temperature.
• E. Incorrect: Strain gauges measure deformation or strain, not temperature.

Correct Answer:

A. Thermocouple

Explanation:

• A. Correct: Thermocouples are commonly used for measuring temperature and can be used for remote reading of a ship’s intermediate shaft bearing temperature.
• B. Incorrect: Strain gauges measure strain, not temperature.
• C. Incorrect: Flowmeters measure fluid flow rates, not temperature.
• D. Incorrect: Pressure transducers measure pressure, not temperature.
• E. Incorrect: Tachometers measure rotational speed, not temperature.

Correct Answer:

A. Linear variable differential transformer (LVDT)

Explanation:

• A. Correct: An LVDT is commonly used for precise and remote position measurement, making it suitable for measuring the position of a diesel engine governor or fuel rack.
• B. Incorrect: Pressure transducers measure pressure, not position.
• C. Incorrect: Thermocouples measure temperature, not position.
• D. Incorrect: Ultrasonic flowmeters measure flow rate, not position.
• E. Incorrect: Proximity sensors detect the presence or absence of an object but are not typically used for precise position measurements.

Correct Answer:

A. Strain gauge

Explanation:

• A. Correct: Strain gauges are used to measure the deformation or strain in materials, including the twist or torsion of a propeller shaft.
• B. Incorrect: Thermocouples measure temperature, not mechanical deformation.
• C. Incorrect: Ultrasonic thickness gauges measure material thickness, not twist or deformation.
• D. Incorrect: Pressure transducers measure pressure, not mechanical deformation.
• E. Incorrect: Flowmeters measure the flow rate of fluids, not mechanical deformation or twist.

Correct Answer:

A. Pressure gauge

Explanation:

• A. Correct: A pressure gauge is designed to measure local pressure readings, making it suitable for measuring the pressure in a ship’s fire-main.
• B. Incorrect: A flowmeter measures flow rate, not pressure.
• C. Incorrect: A thermocouple measures temperature, not pressure.
• D. Incorrect: A strain gauge measures strain, not pressure.
• E. Incorrect: A tachometer measures rotational speed, not pressure.

Correct Answer:

A. Tachometer

Explanation:

• A. Correct: A tachometer is specifically designed to measure rotational speed, making it suitable for measuring the speed of a ship’s main propeller shaft in RPM.
• B. Incorrect: Pressure transducers measure pressure, not rotational speed.
• C. Incorrect: Strain gauges measure strain or deformation, not rotational speed.
• D. Incorrect: Temperature sensors measure temperature, not rotational speed.
• E. Incorrect: Flowmeters measure the flow rate of fluids, not rotational speed.

Correct Answer:

A. Flowmeter

Explanation:

• A. Correct: A flowmeter is specifically designed to measure the flow rate of fluids, making it suitable for measuring the flow rate of a water maker.
• B. Incorrect: A pressure transducer measures pressure, not flow rate.
• C. Incorrect: A thermocouple measures temperature, not flow rate.
• D. Incorrect: A strain gauge measures strain, not flow rate.
• E. Incorrect: A tachometer measures rotational speed, not flow rate.