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Questions and Answers
What are the three main steps in a closed loop industrial control system?
What are the three main steps in a closed loop industrial control system?
What is the primary function of a sensor in a control system?
What is the primary function of a sensor in a control system?
What is a transducer?
What is a transducer?
What type of transducer converts electromagnetic waves into electric current and vice versa?
What type of transducer converts electromagnetic waves into electric current and vice versa?
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What is the function of a tape head?
What is the function of a tape head?
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What type of transducer converts motion into electrical form?
What type of transducer converts motion into electrical form?
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What type of transducer converts changes in light levels into resistance changes?
What type of transducer converts changes in light levels into resistance changes?
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What is a common categorization of transducers?
What is a common categorization of transducers?
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What is the primary function of a sensor?
What is the primary function of a sensor?
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What type of sensor is a thermistor?
What type of sensor is a thermistor?
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What is the purpose of a multiplexer (MUX) in a data acquisition system?
What is the purpose of a multiplexer (MUX) in a data acquisition system?
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What is the role of an excitation circuit in a sensor?
What is the role of an excitation circuit in a sensor?
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What is the main difference between a passive and active sensor?
What is the main difference between a passive and active sensor?
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What is the function of a transducer?
What is the function of a transducer?
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What is the purpose of signal conditioning circuitry in a sensor?
What is the purpose of signal conditioning circuitry in a sensor?
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What is the main function of a sensor?
What is the main function of a sensor?
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What is the role of a data acquisition system?
What is the role of a data acquisition system?
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What is the term for the amount that a sensor's output varies when the measured quantity varies?
What is the term for the amount that a sensor's output varies when the measured quantity varies?
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What type of sensor is a mercury-in-glass thermometer an example of?
What type of sensor is a mercury-in-glass thermometer an example of?
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What is the term for a device that transforms one type of energy into another?
What is the term for a device that transforms one type of energy into another?
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What is an actuator?
What is an actuator?
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What is the main difference between a sensor and a transducer?
What is the main difference between a sensor and a transducer?
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What is the purpose of calibrating a sensor?
What is the purpose of calibrating a sensor?
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Why are smaller sensors often preferred?
Why are smaller sensors often preferred?
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What is the primary difference between contact and non-contact sensors?
What is the primary difference between contact and non-contact sensors?
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What type of sensors detect changes in capacitance?
What type of sensors detect changes in capacitance?
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What is the primary function of an optical proximity sensor?
What is the primary function of an optical proximity sensor?
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What type of transducers convert sound waves into electrical signals?
What type of transducers convert sound waves into electrical signals?
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What is the primary application of Hall effect sensors?
What is the primary application of Hall effect sensors?
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What is the output voltage of a D.C. tachogenerator?
What is the output voltage of a D.C. tachogenerator?
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What is the main advantage of non-contact sensors over contact sensors?
What is the main advantage of non-contact sensors over contact sensors?
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What is the purpose of a photodetector in an optical proximity sensor?
What is the purpose of a photodetector in an optical proximity sensor?
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What is the primary function of contact type switches?
What is the primary function of contact type switches?
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What is the main difference between A.C. and D.C. tachogenerators?
What is the main difference between A.C. and D.C. tachogenerators?
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What is the function of light transducers?
What is the function of light transducers?
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What is the purpose of hall effect sensors?
What is the purpose of hall effect sensors?
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What is the main application of vibration transducers?
What is the main application of vibration transducers?
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What is the function of magnet type switches?
What is the function of magnet type switches?
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What is the purpose of electromagnetic type switches?
What is the purpose of electromagnetic type switches?
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What is the primary function of tachogenerators?
What is the primary function of tachogenerators?
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Study Notes
Introduction to Industrial Control Systems
- A closed-loop industrial control system consists of three steps: applying the input (reference value), controlling the process, and feedback (negative feedback) that measures the output and applies it back to the input stage.
- Sensors are special devices that sense changes in the controlled physical quantity.
- Transducers are devices that convert one type of energy into another.
Types of Transducers
- Electromagnetic transducers:
- Convert electromagnetic waves into electric current and vice versa (e.g., antenna, cathode ray tube (CRT))
- Convert electrical signals into visual form (e.g., CRT)
- Convert electrical power into visible light (e.g., fluorescent lamp, light bulb)
- Electrochemical transducers:
- pH probes
- Electro-galvanic fuel cell
- Hydrogen sensor
- Electromechanical transducers:
- Electro-active polymers
- Galvanometer
- Micro-electromechanical systems (MEMS)
- Rotary motor, linear motor
- Vibration powered generator
- Electrostatic transducers:
- Electrometer
- Photoelectric transducers:
- Laser diode, light-emitting diode (convert electrical power into forms of light)
- Photoresistor, phototransistor, photomultiplier tube (convert changing light levels into electrical form)
- Thermoelectric transducers:
- RTD (Resistance Temperature Detector)
- Photodiode
- Thermocouple
- Peltier cooler
- Thermistor (includes PTC resistor and NTC resistor)
- Electroacoustic transducers:
- Loudspeaker, earphone (convert electrical signals into sound)
- Microphone (convert sound into an electrical signal)
Sensors
- A sensor is a device that uses one type of energy to detect a parameter and report it in another (often an electrical or digital signal).
- Sensors can be classified as:
- Contact sensors: require physical contact with the measured object (e.g., switches, pressure sensors, temperature sensors)
- Non-contact sensors: operate without physical contact with the measured object (e.g., optical sensors, capacitive sensors, inductive sensors)
- Sensors have various applications, including:
- Automation
- Robotics
- Object detection
- Position sensing
- Industrial machinery
- Assembly lines
- Conveyor systems
- Automotive applications
- Consumer electronics
Sensor Characteristics
- Sensitivity: measures the amount of change in the sensor's output when the measured quantity changes
- Sensors can affect the object being measured (e.g., thermometer cooling the liquid, liquid heating the thermometer)
Data Acquisition and Control Systems
- A block schematic of a data acquisition and control device consists of:
- Sensors
- Multiplexer (MUX)
- Analog-to-digital (A/D) converter
- Computer
- Actuator
- Control signals
- The system can include various components and peripheral devices, such as amplifiers, sample-and-hold circuits, filters, and data recorders.
Transducers and Sensors
- Sensors detect physical phenomena and convert them into measurable electrical signals.
- Transducers convert physical quantities into electrical signals.
- Transducers can be classified as:
- Contact type: require physical contact with the measured object
- Non-contact type: operate without physical contact with the measured object
Optical Proximity Sensors
- Basic principle: detect the presence or absence of an object by emitting light and detecting changes in the reflected or transmitted light
- Construction: consist of a light emitter (LED or laser diode) and a photodetector (photodiode or phototransistor) housed in a compact package
- Applications: widely used in automation, robotics, object detection, and position sensing applications
Other Types of Sensors and Transducers
- Switches:
- Contact type switches (e.g., push buttons, limit switches)
- Magnet type switches (e.g., reed switches)
- Electromagnetic type switches (e.g., relays)
- Sound transducers: convert sound waves into electrical signals or vice versa
- Light transducers: convert light energy into electrical signals
- Pressure transducers: measure pressure and convert it into an electrical signal
- Vibration transducers: convert mechanical vibrations into electrical signals
- Hall effect sensors: detect magnetic fields and convert them into electrical signals
- A.C./D.C. tachogenerators: convert rotational speed into electrical signals
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Description
Learn about the basics of closed loop industrial control systems, including the role of sensors and transducers in measuring and controlling physical quantities.