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Questions and Answers
What is a major advantage of absolute encoders compared to incremental encoders?
What is a major advantage of absolute encoders compared to incremental encoders?
What type of code can absolute encoders use for their output?
What type of code can absolute encoders use for their output?
Which statement about the disk of an absolute encoder is true?
Which statement about the disk of an absolute encoder is true?
What problem can occur if the power is momentarily shut off in systems using incremental encoders?
What problem can occur if the power is momentarily shut off in systems using incremental encoders?
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What defines the 'bit'-resolution of an absolute encoder?
What defines the 'bit'-resolution of an absolute encoder?
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What happens to the EMF signals in the two secondary windings when the soft iron magnetic core armature is in the null position?
What happens to the EMF signals in the two secondary windings when the soft iron magnetic core armature is in the null position?
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Which of the following describes the output signal characteristics of an LVDT?
Which of the following describes the output signal characteristics of an LVDT?
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What is one of the advantages of an LVDT compared to a potentiometer?
What is one of the advantages of an LVDT compared to a potentiometer?
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What principle do inductive proximity sensors operate under?
What principle do inductive proximity sensors operate under?
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Which factor is NOT an advantage of using an LVDT?
Which factor is NOT an advantage of using an LVDT?
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What is a typical application of an LVDT?
What is a typical application of an LVDT?
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What type of objects can inductive proximity sensors detect?
What type of objects can inductive proximity sensors detect?
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Which feature is characteristic of the construction of LVDTs for their operation?
Which feature is characteristic of the construction of LVDTs for their operation?
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What is the typical output condition for incremental encoders?
What is the typical output condition for incremental encoders?
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Which type of incremental encoder is known for providing position and velocity information?
Which type of incremental encoder is known for providing position and velocity information?
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How is the direction of rotation determined in a quadrature encoder?
How is the direction of rotation determined in a quadrature encoder?
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What is a primary disadvantage of using incremental encoders?
What is a primary disadvantage of using incremental encoders?
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What outputs are typically produced by a quadrature encoder?
What outputs are typically produced by a quadrature encoder?
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What type of encoder uses two photo detectors offset by 90 degrees?
What type of encoder uses two photo detectors offset by 90 degrees?
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In what application are incremental encoders commonly used?
In what application are incremental encoders commonly used?
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Why is external counting necessary for incremental encoders?
Why is external counting necessary for incremental encoders?
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What phenomenon does the Hall effect describe?
What phenomenon does the Hall effect describe?
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Which of the following is NOT a typical use of Hall effect sensors?
Which of the following is NOT a typical use of Hall effect sensors?
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What distinguishes Eddy Current Based Position Sensors from Hall Effect Based Sensors?
What distinguishes Eddy Current Based Position Sensors from Hall Effect Based Sensors?
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Which factors influence the operation of a Hall effect sensor?
Which factors influence the operation of a Hall effect sensor?
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In the context of eddy current sensors, what happens when a conductive target enters the alternating magnetic field?
In the context of eddy current sensors, what happens when a conductive target enters the alternating magnetic field?
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What is a key advantage of using non-contact devices like Hall effect sensors?
What is a key advantage of using non-contact devices like Hall effect sensors?
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Eddy currents produced in conductive materials oppose which type of field?
Eddy currents produced in conductive materials oppose which type of field?
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Which statement about Hall effect sensors is true?
Which statement about Hall effect sensors is true?
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Which characteristic makes fiber optic position sensors effective in harsh environments?
Which characteristic makes fiber optic position sensors effective in harsh environments?
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What are the two types of fiber optic sensors?
What are the two types of fiber optic sensors?
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What measurement is a fiber optic sensor primarily used to detect?
What measurement is a fiber optic sensor primarily used to detect?
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In intrinsic fiber optic sensors, what aspect of the fiber modulates the measurand?
In intrinsic fiber optic sensors, what aspect of the fiber modulates the measurand?
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Which field of application is NOT typically associated with fiber optic position sensors?
Which field of application is NOT typically associated with fiber optic position sensors?
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What is a primary advantage of using fiber optic position sensors in multiplexing signals?
What is a primary advantage of using fiber optic position sensors in multiplexing signals?
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How is temperature defined in physical terms?
How is temperature defined in physical terms?
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What kind of physical parameters can fiber optic sensors measure?
What kind of physical parameters can fiber optic sensors measure?
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Study Notes
LVDT (Linear Variable Differential Transformer)
- A small AC reference voltage (called the "excitation signal") is applied to the primary winding.
- The excitation signal induces an EMF signal into the two adjacent secondary windings.
- The output voltage is zero when the core is in the center (null position) because the induced EMFs in the secondary windings cancel each other out.
- Output signal amplitude is a linear function of the core's displacement.
- Output signal polarity indicates the direction of movement.
- Advantages over potentiometers: excellent voltage output to displacement, high accuracy, resolution, sensitivity, frictionless operation, and sealed for use in hostile environments.
Inductive Proximity Sensor
- Detects ferrous and non-ferrous metal objects.
- Operates based on Faraday's Law of inductance.
- Consists of an oscillator, a coil, and a sensing circuit.
- Does not detect non-metallic objects.
Hall Effect Based Magnetic Position Sensors
- Determines object position by detecting magnetic fields generated from various sources (Earth, electric currents, magnets, brain waves).
- Functions based on the Hall Effect: a voltage is generated perpendicular to both current and magnetic field when a current-carrying conductor is placed in a magnetic field.
Eddy Current Based Position Sensors
- Non-contact devices that measure position, displacement, oscillation, and vibration of conductive targets.
- Require high precision and can operate in harsh environments.
- Function based on magnetic induction:
- An alternating current passed through a coil generates an alternating magnetic field.
- When a target comes into contact with this field, eddy currents are induced in the target.
- Eddy currents create a field opposing the sensor's field, resulting in an output signal.
Incremental Encoders
- Convert mechanical motion into digital information.
- Available in two types:
- Single channel encoder: Provides position and velocity information.
- Quadrature or Sine wave encoder: Produces two separate sine and cosine output signals.
- Direction of rotation is determined by which channel produces an output first, either channel A or channel B.
- Main disadvantage: Requires external counters to determine absolute angle, making them susceptible to errors if power is interrupted or pulses are missed.
Absolute Encoders
- Output is an absolute measure of position, indicating the current position of the shaft.
- Provide a unique output code for every position.
- Coded disk consists of multiple tracks of light and dark segments, each with its own photo detector to read a unique coded position value.
- Number of tracks corresponds to the encoder's resolution.
Fiber Optic Position Sensors
- Use optical fibers as the sensing device.
- Sense temperature, strain, pressure, displacement, velocity, and acceleration.
- Based on retro reflectance of light inside an optical fiber due to the movement of the proximal mirror surface.
- Immune to electromagnetic radiation, magnetic fields, lightning, and harsh environmental conditions.
- Two types:
- Intrinsic sensors: The measurand modulates the transmission properties of the optical fiber (intensity, polarization, phase).
- Extrinsic sensors: Modulation occurs outside the fiber, using the fiber as a conduit for light.
- Advantages: Immune to electromagnetic radiation, electrically insulating, wide temperature range, and ability to multiplex signals.
Temperature Sensors
- Temperature is the most widely sensed parameter due to its impact on materials and processes at the molecular level.
- Defined as the degree of hotness or coldness relative to a specific scale, or the amount of heat energy in a system or object.
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Description
Test your knowledge on LVDT, inductive proximity sensors, and Hall effect magnetic position sensors. This quiz covers the principles, advantages, and operational mechanisms of these essential electromechanical devices. Enhance your understanding of how these sensors function in various applications.