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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 ______.
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.
In a Wheatstone bridge, small changes in ______ are measured for sensors.
In a Wheatstone bridge, small changes in ______ are measured for sensors.
The typical materials for RTD devices include platinum, nickel, and ______.
The typical materials for RTD devices include platinum, nickel, and ______.
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 ______.
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.
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 ______.
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.
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.
A phototransistor is a ______-sensitive transistor.
A phototransistor is a ______-sensitive transistor.
A digital optical encoder converts motion into a sequence of digital ______.
A digital optical encoder converts motion into a sequence of digital ______.
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.
A photoelectric sensor emits a light beam from its ______ element.
A photoelectric sensor emits a light beam from its ______ element.
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.
An ______ is a small mass-spring-damper system with high natural frequency.
An ______ is a small mass-spring-damper system with high natural frequency.
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.
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.
MEMS stands for micro-______-mechanical systems.
MEMS stands for micro-______-mechanical systems.
MEMS can range in size from a few micrometers to ______.
MEMS can range in size from a few micrometers to ______.
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.
Both mechanical microstructures and ______ are part of MEMS technology.
Both mechanical microstructures and ______ are part of MEMS technology.
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.
Transducers that convert physical quantities into electrical signals are called _____ transducers.
Transducers that convert physical quantities into electrical signals are called _____ transducers.
Active sensors require an external power source called an _____ signal.
Active sensors require an external power source called an _____ signal.
Examples of passive sensors include the _____ sensor and thermocouple.
Examples of passive sensors include the _____ sensor and thermocouple.
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 _____ .
Linear variable differential transformers (LVDT) are used to measure _____ .
Linear variable differential transformers (LVDT) are used to measure _____ .
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.
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.
A tactile sensor is also known as a ________ sensor.
A tactile sensor is also known as a ________ sensor.
One of the most widely used forms of light sensor is the ________.
One of the most widely used forms of light sensor is the ________.
Sensors and actuators are both examples of ________.
Sensors and actuators are both examples of ________.
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 ________.
The form of displacement sensors shown here is known as ________.
The form of displacement sensors shown here is known as ________.
All mechanical switches suffer from ________ bounce.
All mechanical switches suffer from ________ bounce.
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 ________.
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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