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Questions and Answers
A thermocouple consists of two junctions made from unlike conductors such as iron and ______.
A thermocouple consists of two junctions made from unlike conductors such as iron and ______.
constantan
The materials used in CHROMEL are 90% nickel and 10% ______.
The materials used in CHROMEL are 90% nickel and 10% ______.
chromium
Resistance Temperature Detectors (RTDs) are constructed of metallic wire wound around a ceramic or ______ core.
Resistance Temperature Detectors (RTDs) are constructed of metallic wire wound around a ceramic or ______ core.
glass
The resistance of metallic wire in an RTD increases with ______.
The resistance of metallic wire in an RTD increases with ______.
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The ______ bridge circuit is commonly used to convert resistance changes into voltage changes.
The ______ bridge circuit is commonly used to convert resistance changes into voltage changes.
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In a Wheatstone bridge, small changes in ______ are measured for sensors.
In a Wheatstone bridge, small changes in ______ are measured for sensors.
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The typical materials for RTD devices include platinum, nickel, and ______.
The typical materials for RTD devices include platinum, nickel, and ______.
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The resistance change in RTDs can be related to temperature with a temperature coefficient denoted as ______.
The resistance change in RTDs can be related to temperature with a temperature coefficient denoted as ______.
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The sensing methods may rely on direct methods of transduction from light to electrical quantities such as in photovoltaic sensors or indirect methods such as conversion first into ______ variation.
The sensing methods may rely on direct methods of transduction from light to electrical quantities such as in photovoltaic sensors or indirect methods such as conversion first into ______ variation.
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A Light Dependent Resistor (LDR) is a widely used photo sensor whose resistance is inversely proportional to the intensity of ______.
A Light Dependent Resistor (LDR) is a widely used photo sensor whose resistance is inversely proportional to the intensity of ______.
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When light is detected by the LDR, its resistance changes causing the ______ to trigger that activates the relay.
When light is detected by the LDR, its resistance changes causing the ______ to trigger that activates the relay.
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The construction of the photodiode light sensor is similar to that of a conventional ______-junction diode.
The construction of the photodiode light sensor is similar to that of a conventional ______-junction diode.
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A phototransistor is a ______-sensitive transistor.
A phototransistor is a ______-sensitive transistor.
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A digital optical encoder converts motion into a sequence of digital ______.
A digital optical encoder converts motion into a sequence of digital ______.
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Rotary encoders can be either absolute encoders or ______ encoders, which produce digital pulses as the shaft rotates.
Rotary encoders can be either absolute encoders or ______ encoders, which produce digital pulses as the shaft rotates.
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A photoelectric sensor emits a light beam from its ______ element.
A photoelectric sensor emits a light beam from its ______ element.
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Some materials, called ______, produce a charge in response to a force applied to them.
Some materials, called ______, produce a charge in response to a force applied to them.
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An ______ is a small mass-spring-damper system with high natural frequency.
An ______ is a small mass-spring-damper system with high natural frequency.
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A simple magnetic accelerometer uses a permanent magnet as a ______ on a spring.
A simple magnetic accelerometer uses a permanent magnet as a ______ on a spring.
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A load cell converts a load or force acting on it into an ______ signal.
A load cell converts a load or force acting on it into an ______ signal.
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MEMS stands for micro-______-mechanical systems.
MEMS stands for micro-______-mechanical systems.
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MEMS can range in size from a few micrometers to ______.
MEMS can range in size from a few micrometers to ______.
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The ability of MEMS to sense, control, and ______ on the micro scale is significant.
The ability of MEMS to sense, control, and ______ on the micro scale is significant.
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Both mechanical microstructures and ______ are part of MEMS technology.
Both mechanical microstructures and ______ are part of MEMS technology.
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A sensor detects the magnitude of a physical parameter and changes it into a signal that can be processed by the _____ system.
A sensor detects the magnitude of a physical parameter and changes it into a signal that can be processed by the _____ system.
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Transducers that convert physical quantities into electrical signals are called _____ transducers.
Transducers that convert physical quantities into electrical signals are called _____ transducers.
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Active sensors require an external power source called an _____ signal.
Active sensors require an external power source called an _____ signal.
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Examples of passive sensors include the _____ sensor and thermocouple.
Examples of passive sensors include the _____ sensor and thermocouple.
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The Seebeck effect refers to the voltage produced when temperature changes at the junction formed by joining two unlike _____ .
The Seebeck effect refers to the voltage produced when temperature changes at the junction formed by joining two unlike _____ .
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Linear variable differential transformers (LVDT) are used to measure _____ .
Linear variable differential transformers (LVDT) are used to measure _____ .
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A classical thermometer does not provide an output signal that can be inputted to a _____ for further use.
A classical thermometer does not provide an output signal that can be inputted to a _____ for further use.
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Monitoring and control systems utilize sensors to measure physical quantities such as position, distance, force, _____ , temperature, vibration, and acceleration.
Monitoring and control systems utilize sensors to measure physical quantities such as position, distance, force, _____ , temperature, vibration, and acceleration.
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A tactile sensor is also known as a ________ sensor.
A tactile sensor is also known as a ________ sensor.
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One of the most widely used forms of light sensor is the ________.
One of the most widely used forms of light sensor is the ________.
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Sensors and actuators are both examples of ________.
Sensors and actuators are both examples of ________.
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The maximum expected error associated with a measurement or a sensor is known as ________.
The maximum expected error associated with a measurement or a sensor is known as ________.
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The form of displacement sensors shown here is known as ________.
The form of displacement sensors shown here is known as ________.
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All mechanical switches suffer from ________ bounce.
All mechanical switches suffer from ________ bounce.
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A form of temperature sensor that produces a large change in resistance with temperature is a ________.
A form of temperature sensor that produces a large change in resistance with temperature is a ________.
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The type of temperature sensor most likely found in an Integrated Circuit is a ________ based sensor.
The type of temperature sensor most likely found in an Integrated Circuit is a ________ based sensor.
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Study Notes
Sensors Overview
- Sensors convert physical parameters like distance, force, temperature, etc. into a signal that can be processed by a system.
- Transducers are the active element of sensors converting energy from one form to another.
Sensor Types
- Active Sensors: Use an external power source (excitation signal) to operate; examples: Photoelectric sensors.
- Passive Sensors: Generate electric current in response to an external stimulus without needing additional energy; examples: Piezoelectric sensor and thermocouple.
Temperature Sensors
- Thermocouple: Two dissimilar conductors are joined to create a junction; temperature changes cause electron reconfiguration and produce voltage (Seebeck effect).
- Resistance Temperature Detectors (RTDs): Metal wire wound around a core which changes resistance based on temperature; common materials include platinum, nickel, and copper.
Wheatstone Bridge Circuit
- Used to measure small changes in resistance, often from sensors.
- Converts resistance change to voltage change.
- Commonly used with RTDs and other sensors.
Light Sensors
- Light Dependent Resistor (LDR): Resistance changes inversely with light intensity; common for light sensitive switches.
- Photodiode: A PN-junction diode sensitive to light, particularly longer wavelengths like red and infrared.
- Photo-transistor: A light-sensitive transistor where light reaches the base-collector junction.
Optical Encoder
- Converts motion into a sequence of digital pulses.
- Used to measure relative or absolute position.
- Two types: Absolute (unique digital word for each position) and Incremental (digital pulses for relative displacement).
Photoelectric Sensors
- Emit a light beam and detect it; used for proximity detection.
- Reflective: light is reflected back from the target.
Accelerometers
- Piezoelectric: Some materials generate a charge in response to applied force.
- Inertial: Mass-spring-damper system that vibrates based on acceleration; used to measure acceleration.
- Magnetic: Uses a permanent magnet and sensor (Hall effect or magnetoresistive) to measure the magnet’s position based on acceleration.
Load Cell
- Transducer that converts force into an electronic signal (voltage, current, or frequency).
Potentiometer
- Used to measure position or displacement.
- A variable resistor that changes the resistance based on a moving contact.
MEMS (Micro-electromechanical Systems)
- Tiny integrated devices integrating mechanical and electrical components.
- Fabricated using IC batch processing techniques.
- Used in mobile phones, car sensors, and other applications.
Self-Assessment Questions
- Question 1: Sensors and transducers are both examples of transducers.
- Question 2: Accuracy is the maximum expected error.
- Question 3: Thermistor.
- Question 4: A photodiode is an example of a photovoltaic sensor.
- Question 5: Vertical.
- Question 6: Potentiometers.
- Question 7: A slotted opto-switch.
- Question 8: True.
- Question 9: Pressure.
- Question 10: Semiconductor-based sensor.
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Description
This quiz covers the fundamentals of sensors and their categories, including active and passive sensors. Discover how temperature sensors like thermocouples and RTDs function, as well as the role of Wheatstone bridge circuits in measuring resistance changes.
