40 Questions
What does an accelerometer measure?
Acceleration
Which of the following devices is an example of a thermoelectric sensor?
Thermocouple
What is the primary function of a sensor?
To transform a physical quantity into a signal
What is the term for the amount that a sensor's output varies when the measured quantity varies?
Sensitivity
Which type of sensor is a mercury-in-glass thermometer?
Thermomechanical
What is the primary difference between a sensor and a transducer?
A sensor transforms a signal into an electrical signal, while a transducer transforms one type of energy into another
What is the primary function of sensors in a closed loop industrial control system?
To measure changes in the controlled physical quantity
What is the purpose of calibrating a sensor?
To ensure the sensor's accuracy against recognized standards
What type of energy conversion is possible with a transducer?
Electrical, electro-mechanical, electromagnetic, photonic, photovoltaic, or any other form of energy
What is the advantage of using smaller sensors?
They have a negligible impact on the object being measured
What is the primary application of a Cathode Ray Tube (CRT)?
To convert electrical signals into visual form
What is the function of a Hall effect sensor?
To convert a magnetic field level into electrical form
What is the primary function of a transducer?
To convert one type of energy to another
What is the primary application of a photo-detector or Photo-resistor (LDR)?
To convert changes in light levels into resistance changes
What is the primary application of a magnetic cartridge?
To convert motion into electrical form
What is the primary function of a fluorescent lamp?
To convert electrical power into visible light
What is the primary function of transducers in the context of sensors?
To convert physical quantities into electrical signals
What is the main difference between contact and non-contact sensors?
Contact sensors require physical contact, while non-contact sensors do not
What type of sensors use infrared or visible light sources and photodetectors to detect the presence or absence of an object?
Optical proximity sensors
What is the typical application of tachogenerators?
Speed measurement and control in industrial machinery
What type of switches detect physical contact or position changes?
Contact type switches
What type of transducers convert sound waves into electrical signals?
Sound transducers
What is the primary function of Hall effect sensors?
To detect magnetic fields
What is the main advantage of non-contact sensors over contact sensors?
Minimizing wear and damage
What is the primary advantage of micro-sensors employing MEMS technology compared to macroscopic methods?
Far higher speed and sensitivity
What is the primary function of sensor 5 in a data acquisition system?
To monitor the internal workings of the data acquisition system
What is the primary difference between passive and active sensors?
Passive sensors produce electric signals without using energy from the electrical circuitry
What is the primary function of a multiplexer (MUX) in a data acquisition system?
To link each sensor individually to a direct analog-to-digital converter or a computer
What is the primary application of sensors and transducers in modern technology?
To enable the monitoring and control of physical parameters in industrial processes
What is the primary function of sensing elements in sensors?
To detect physical phenomena and convert them into measurable electrical signals
What is the primary difference between a thermistor and a thermocouple?
A thermistor is a passive sensor, while a thermocouple is an active sensor
What is the primary function of a transducer in a data acquisition system?
To convert one form of energy into another
What is the primary function of contact type switches?
Physically making or breaking contact between conducting elements
Which type of transducer converts sound waves into electrical signals or vice versa?
Sound transducer
What is the primary application of Hall effect sensors?
Proximity sensing, speed measurement, and current sensing
What is the main difference between A.C. and D.C. tachogenerators?
The output signal frequency
Which type of switch uses the presence or absence of a magnetic field to open or close electrical contacts?
Magnet type switch
What is the primary function of transducers in electronic systems?
To convert one form of energy into another
What is the application of vibration transducers?
Vibration analysis, condition monitoring, and structural health monitoring
What is the primary function of tachogenerators?
To convert rotational speed into electrical signals
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
Understand the components of a closed-loop industrial control system, including input, control, and feedback stages. Learn about sensors and transducers, and their roles in measuring physical quantities and converting energy types.
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