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Questions and Answers
What is the primary function of an LVDT?
What is the primary function of an LVDT?
Why must side loads be avoided in an LVDT?
Why must side loads be avoided in an LVDT?
What is the recommended frequency for the input voltage in an LVDT relative to the desired frequency response?
What is the recommended frequency for the input voltage in an LVDT relative to the desired frequency response?
What does the formula $ heta = rac{T L}{
u d^{4} K'}$ relate to in torque measurement?
What does the formula $ heta = rac{T L}{ u d^{4} K'}$ relate to in torque measurement?
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Which application is NOT typically associated with an electromagnetic linear-velocity transducer?
Which application is NOT typically associated with an electromagnetic linear-velocity transducer?
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How is the output voltage in an LVDT primarily affected?
How is the output voltage in an LVDT primarily affected?
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What is a significant characteristic of photoelectric sensors regarding response time?
What is a significant characteristic of photoelectric sensors regarding response time?
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Which type of optical proximity sensor has the transmitter and receiver in the same package?
Which type of optical proximity sensor has the transmitter and receiver in the same package?
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What phenomenon is utilized in a magnetic core linear-velocity transducer to measure speed?
What phenomenon is utilized in a magnetic core linear-velocity transducer to measure speed?
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In the context of LVDTs, what would happen if the core were to bend?
In the context of LVDTs, what would happen if the core were to bend?
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In the Hall Effect sensor, what effect does the magnet have on the current?
In the Hall Effect sensor, what effect does the magnet have on the current?
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What type of feedback mechanism is indicated for force measurement applications in conjunction with LVDT?
What type of feedback mechanism is indicated for force measurement applications in conjunction with LVDT?
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What is the output behavior of an LVDT when the magnetic core is near the center of the coils?
What is the output behavior of an LVDT when the magnetic core is near the center of the coils?
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The delay in current conduction for photoelectric sensors is mainly due to what?
The delay in current conduction for photoelectric sensors is mainly due to what?
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What role does the nonmagnetic push rod play in an LVDT?
What role does the nonmagnetic push rod play in an LVDT?
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Which statement about retro-reflective optical sensors is correct?
Which statement about retro-reflective optical sensors is correct?
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Which type of non-contact sensor is specifically designed to detect electrically conductive materials?
Which type of non-contact sensor is specifically designed to detect electrically conductive materials?
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What is a key component of how a capacitive proximity sensor operates?
What is a key component of how a capacitive proximity sensor operates?
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What distinguishes proximity sensors from true switches in terms of operation?
What distinguishes proximity sensors from true switches in terms of operation?
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In which scenario would an optical proximity sensor be most appropriate to use?
In which scenario would an optical proximity sensor be most appropriate to use?
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What phenomenon does an inductive proximity sensor rely on to detect conductive materials?
What phenomenon does an inductive proximity sensor rely on to detect conductive materials?
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How does the internal circuitry of a proximity sensor function when the output reaches a certain value?
How does the internal circuitry of a proximity sensor function when the output reaches a certain value?
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Which proximity sensor can detect almost any object regardless of its material properties?
Which proximity sensor can detect almost any object regardless of its material properties?
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What metric can be evaluated by the change in capacitance in a capacitive proximity sensor?
What metric can be evaluated by the change in capacitance in a capacitive proximity sensor?
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Study Notes
Switches and Displacement Sensors
- Non-contact sensors are transducers with control circuitry. The circuitry acts as a switch when the transducer output reaches a threshold value.
- Three common types of non-contact sensors are inductive, capacitive, and optical proximity sensors.
- Proximity sensors use a small amount of current for operation unlike a traditional switch.
Inductive Proximity Sensor
- Detects electrically conductive materials.
- Eddy currents in the conductive material affect the AC impedance in the sensor, causing a drop in internal AC current.
- Components include: sensing face, magnetic field coil, oscillator, demodulator, output amplifier, and Schmitt trigger.
Capacitive Proximity Sensors
- Works on the principle of electrical charge that's almost any object.
- A change in spacing between the sensor's internal plates changes capacitance. This affects the current between plates & determines proximity.
- Components include: oscillator to create AC, internal capacitor plate, effective capacitor plate (in the target), and current sensor to measure changes.
Optical Proximity Sensors (Thru-Beam)
- Measures light changes detected by the sensor, that aren't likely from nearby sources.
- Consists of a transmitter and receiver; light beam travels through the gap.
- Dependent on light generated at a frequency specific & different from nearby light sources, and have a delay between light detection and current conduction.
Photoelectric Sensors
- Types: triangulation (light reflected from a target in different positions), reflective (light reflected), and retro-reflective sensors (light travels to a target and returns)
- Components include transmitters/emitters and receivers (detectors).
Optical Proximity Sensors (Retroreflective)
- Transmitter & receiver in one package.
- Light beam is reflected by a target back to the receiver.
Hall Effect Sensor
- Measures changes in current when a magnet is moved relative to a sensor.
- Current is directed to one side.
- Generates a voltage proportional to magnet proximity.
LVDT (Linear Variable Differential Transformer)
- Measures linear displacement.
- Alternating input voltage in a center coil generates output voltage in the two end coils; amount/phase changes based on core position.
- Frequency should be 10 times desired frequency for desired response.
- Affected by inertia characteristics.
- Side loads cause armature/core motion friction and potential bending.
Electromagnetic Linear Velocity Transducer
- Measures the velocity of an object via a moving core.
- Changes in magnetic field create current.
Velocity Transducer
- Uses a moving coil beside a stationary magnet.
- Relative motion between magnetic field & coil causes a proportional current; proportional to the velocity.
- No excitation is needed.
Velometer/Accelerometer-Electronic Integrator
- An accelerometer with built-in electronic integrator.
- Relatively heavy & complex sensor
- Poor frequency response (< 1000 Hz)
Measurement of Force and Torque (Electrodynamic Feedback Load Cell)
- Measures force using current proportional to downward displacement & an LVDT (linear variable differential transducer)
- Weighs very light objects (0.1 mg ~ 100 g).
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Description
Test your knowledge on non-contact sensors, including inductive and capacitive proximity sensors. Understand how these sensors operate and their essential components. Challenge yourself with questions that cover key concepts in sensor technology.
