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Questions and Answers

What is one of the main applications of a Digital Storage Oscilloscope (DSO)?

  • Displays 3D figures or multiple waveforms (correct)
  • Converts energy from one form to another
  • Measures electrical resistance
  • Tests the longevity of electronic components

    • Passive transducers can generate their own output signal without external power.

    False

    List two advantages of using a Digital Storage Oscilloscope (DSO).

    Portable, high bandwidth

    A transducer that derives power from an external source is termed a ______ transducer.

    <p>passive</p> Signup and view all the answers

    Match the following types of transducers with their definitions:

    <p>Active transducer = Self-generating type that develops its own signal Passive transducer = Externally powered and derives power from another source DSO = Digital Storage Oscilloscope used for measuring Transducer = Device that converts energy from one form to another</p> Signup and view all the answers

    Which of the following is a disadvantage of using a Digital Storage Oscilloscope (DSO)?

    <p>High cost</p> Signup and view all the answers

    The basic requirements of a transducer include linearity, ruggedness, and repeatability.

    <p>True</p> Signup and view all the answers

    What is the main function of a transducer?

    <p>To convert energy from one form to another</p> Signup and view all the answers

    What is measured in AC Current Mode after AC to DC conversion?

    <p>Drop across an internal calibrated shunt</p> Signup and view all the answers

    A Digital Storage Oscilloscope can only display signals in real-time and does not have a storage capability.

    <p>False</p> Signup and view all the answers

    Name two factors that determine the maximum frequency measured on a digital signal oscilloscope.

    <p>Sampling rate and nature of the converter</p> Signup and view all the answers

    In Resistance Mode, the digital multimeter measures the voltage across the ______, resulting from a current flowing through it.

    <p>externally connected resistor</p> Signup and view all the answers

    Match the components of a Digital Storage Oscilloscope with their functions:

    <p>Amplifier = Boosts weak signals Digitizer = Converts analog to digital signals Memory = Stores digitized waveforms Analyzer Circuitry = Processes the digital signal</p> Signup and view all the answers

    Which of the following is NOT a special function of a Digital Multimeter (DMM)?

    <p>Waveform reconstruction</p> Signup and view all the answers

    The vertical input signal in a cathode ray tube (CRT) represents the Y-axis.

    <p>True</p> Signup and view all the answers

    What is the purpose of the time base circuitry in a Digital Storage Oscilloscope?

    <p>To generate the time base signal which is a ramp signal.</p> Signup and view all the answers

    What principle do most pressure sensors operate on?

    <p>Piezo-resistive effect</p> Signup and view all the answers

    Strain gauges only work under tensile forces.

    <p>False</p> Signup and view all the answers

    What materials are commonly used to make the body of pressure sensors?

    <p>Aluminum or stainless steel</p> Signup and view all the answers

    The change in electrical resistance in a strain gauge is caused by the applied ______.

    <p>strain</p> Signup and view all the answers

    Match the elements related to pressure sensors with their functions:

    <p>Strain gauge = Measures variations in resistance Wheatstone Bridge = Converts low strength signals Signal conditioner = Amplifies and filters signals Flexure = Provides mechanical support</p> Signup and view all the answers

    What important function does a pressure sensor signal conditioner perform?

    <p>It converts the signal into a more useful form</p> Signup and view all the answers

    The output signal of a pressure sensor is directly proportional to the force applied to the flexure.

    <p>True</p> Signup and view all the answers

    What is the primary purpose of a strain gauge?

    <p>To measure force, pressure, or strain by varying electrical resistance</p> Signup and view all the answers

    What is the primary function of the Hall effect transducer?

    <p>To measure the current without physical connection</p> Signup and view all the answers

    The intensity of the magnetic field in Hall effect transducers is inversely proportional to the applied current.

    <p>False</p> Signup and view all the answers

    What effect does the Hall effect transducer use to measure power?

    <p>The induced voltage across the strip is proportional to the power.</p> Signup and view all the answers

    A photoelectric transducer converts light energy to __________ energy.

    <p>electrical</p> Signup and view all the answers

    Match the following types of photoelectric transducers with their descriptions:

    <p>Photoemissive Cell = Emits electrons when light radiation hits Photodiode = Generates current based on light exposure Phototransistor = Acts as a switch influenced by light Photovoltaic Cell = Generates voltage related to light intensity Photoconductive Cell = Changes resistance based on light exposure</p> Signup and view all the answers

    Which of the following is NOT a type of photoelectric transducer?

    <p>Thermistor</p> Signup and view all the answers

    The flow of current from a photoelectric transducer depends solely on the temperature.

    <p>False</p> Signup and view all the answers

    How does light absorption affect the semiconductor in a photoelectric transducer?

    <p>It boosts electrons, generating changes in resistance, output current, and voltage.</p> Signup and view all the answers

    Which of the following is NOT an advantage of LCDs?

    <p>Requires additional light sources</p> Signup and view all the answers

    LCD screens consume more power than CRT displays.

    <p>False</p> Signup and view all the answers

    Name two applications of LCDs.

    <p>LCD televisions, computer monitors</p> Signup and view all the answers

    An LCD screen is commonly used in a ___________ for displaying information.

    <p>television</p> Signup and view all the answers

    Match the type of proximity sensor with its suitable target:

    <p>Capacitive Proximity Sensor = Plastic target Inductive Proximity Sensor = Metal target Photoelectric Sensor = Glass target Ultrasonic Sensor = Liquid target</p> Signup and view all the answers

    Which of the following statements about inductive proximity sensors is true?

    <p>They require a metal target to operate.</p> Signup and view all the answers

    Liquid crystal displays are gradually being replaced by OLED technology.

    <p>True</p> Signup and view all the answers

    What limits the operational range of LCDs?

    <p>Temperature</p> Signup and view all the answers

    What is the primary function of an optocoupler?

    <p>To transfer electrical signals between isolated circuits using light</p> Signup and view all the answers

    An optocoupler can only be used with AC signals.

    <p>False</p> Signup and view all the answers

    What are the two main components of an optocoupler?

    <p>LED and photosensitive device</p> Signup and view all the answers

    Optocouplers are commonly used to isolate low-voltage devices from __________ circuits.

    <p>high-voltage</p> Signup and view all the answers

    Which type of photosensitive device is NOT typically found in an optocoupler?

    <p>Photo-resistor</p> Signup and view all the answers

    Match the type of optocoupler with its typical application:

    <p>Photo-transistor = DC circuits Photo-Darlington = DC circuits Photo-SCR = Control AC circuits Photo-TRIAC = Control AC circuits</p> Signup and view all the answers

    What is one advantage of using optocouplers?

    <p>Electrical isolation provides circuit protection.</p> Signup and view all the answers

    Optocouplers have a high operational speed.

    <p>False</p> Signup and view all the answers

    Study Notes

    Unit 4 - Transducers and Sensors

    • Basic principles and classification of Instruments: Moving coil instruments, moving iron instruments, digital multimeter, digital storage oscilloscope.
    • Transducer Classification: Capacitive, inductive, LVDT (Linear Variable Differential Transformer), thermistors, thermocouple, piezoelectric transducers, photoelectric transducers, Hall effect transducers.
    • Opto-electronics Devices: Light Dependent Resistor (LDR), photodiodes, phototransistors, photovoltaic cells (solar cells), optocouplers, liquid crystal display (LCD), proximity sensor, IR sensor, bio sensor.
    • Sensors for smart building: Introduction to sensors used in building automation, such as for security, energy management, temperature regulation.

    Classification of Instruments

    • Methods of Classification: By the quantity measured (e.g., voltmeter, ammeter), by the principles used for their working (e.g., moving iron), and by the method of measurement used (e.g., deflecting).
    • Deflecting Torque: The torque acting on the instrument's moving system to cause the required deflection, proportional to the magnitude of the measured quantity.
    • Opposing Torques:
      • Inertia Torque: Due to the moving system's inertia, the deflecting torque must overcome this.
      • Control Torque: Always present, opposing the deflecting torque, and essential to return the system to zero position after disconnection. It's usually produced by springs or gravity.
      • Damping Torque: Produced during instrument operation, ensuring the moving system reaches its final position in the required time.

    Moving Coil Instruments (PMMC)

    • Principle: A current-carrying coil placed in a magnetic field experiences a force, causing it to rotate.
    • Construction: A permanent magnet, soft iron core, coil of many turns, spindle, helical springs, and pointer.
    • Working: The magnetic field from the permanent magnet interacts with the current in the coil, producing a torque proportional to the current or voltage being measured. The pointer indicates the value on a calibrated scale.
    • Deflecting Torque, Control Torque & Damping Torque: Deflecting torque is proportional to current, control torque provided by springs, and damping due to eddy currents.

    Dynamometer Type Moving Coil Instrument

    • Principle: The operating fields are produced by currents, not permanent magnets. Both fixed and moving coils carry current.
    • Construction: Fixed coil in two sections, a moving coil placed between them, spindle, pointer, calibrated scale. Spring for control torque. Piston inside air chamber to create damping.
    • Working: The interaction between the currents and magnetic fields in the fixed and moving coils creates a deflecting torque proportional to the square of the voltage or current measured.
    • Deflecting Torque, Control Torque & Damping Torque: Deflecting torque proportional to current squared, control torque provided by springs, damping by air friction.

    Moving Iron Instruments (Attraction & Repulsion Type)

    • Principle: A soft iron piece (armature) is placed in the magnetic field produced by the current carrying coil. The movement due to attraction/repulsion forces proportionally to the square of the current or voltage.
    • Construction: A working coil, soft iron disc/armature, spindle with pointer on a calibrated scale, control torque by spring/gravity.
    • Working: The current in the coil produces a magnetic field, thus the magnetic field magnetizes the soft iron disc towards or away from the centre of the coil, causing it to rotate. The pointer indicates the value on a calibrated scale.
    • Deflecting Torque, Control Torque & Damping Torque: Deflecting torque proportional to square of the current, control torque provided by springs/gravity, damping by air friction.

    Digital Multimeter (DMM)

    • Principle: Measures voltage, current, and resistance using digital display. Combines multiple meters in one device.
    • Construction: Constant current source, rotary switch, input probes, buffer amplifier, calibrated attenuator, rectifier circuit, Analog to Digital converter, digital display.
    • Working: The input is routed to the appropriate circuit based on settings, which feeds the result to the display.
    • Advantages & Disadvantages: Advantages are high accuracy, zero parallax error, digital output. Disadvantages include poor response to fluctuating measurements, more expensive, can be difficult to find specific models.
    • Special Functions: Continuity test, diode test, battery test.

    Digital Storage Oscilloscope (DSO)

    • Principle: Stores a digital copy of the waveform for signal analysis, including signal processing.
    • Construction: Amplifier, digitizer, memory, analyzer circuitry, waveform reconstruction, horizontal amplifier, time base circuitry, trigger, and clock.
    • Working: The input signal is amplified, digitized, stored in memory, and processed by the analyzer circuit. The processed data is converted back into an analog form. This signal is applied to the CRT, displaying the waveform on screen.
    • Advantages & Disadvantages: High accuracy, fast analysis, minimal error. Disadvantages include expensive, performance can be influenced if the sampling rate is not appropriate for the signal being measured.

    Basic Requirements of a Transducer

    • Linearity: Input-output characteristics should be linear.
    • Ruggedness: Should withstand overloads with protective measures.
    • Repeatability: Produces identical signals for same input under same conditions.
    • High Stability and Reliability: The output should not be affected by temperature, vibrations, etc., with minimum error.
    • Good Dynamic Response: Should respond efficiently to input variations.
    • Convenient Instrumentation: The signal should be strong enough to be measured.
    • Good Mechanical Characteristics: Should maintain their form and not deform under conditions.

    Active and Passive Transducers

    • Active Transducers: Develop their own output voltage or current from the input signal/energy. e.g., thermocouples, piezoelectric transducers.
    • Passive Transducers: Require an external power source to convert input signal into an output. e.g., potentiometer, resistance strain gauges.

    Other Sensor Types

    • Thermocouples: Measure temperature differences based on the Seebeck effect.
    • Piezoelectric Transducers: Convert pressure, force, acceleration, into electrical signals.
    • Hall Effect Transducers: Measure magnetic fields.
    • Light-Dependent Resistors (LDRs): Resistance changes in response to light.
    • Photodiodes: Generate current in response to light incidence, typically in reverse bias.
    • Phototransistors: Amplify the photocurrent signal, commonly used in light detection.
    • Photovoltaic Cells (Solar Cells): Convert light into direct current energy.
    • Optocouplers: Provide electrical isolation between circuits using light.
    • Liquid Crystal Displays (LCDs): Modulate light to create images and text.
    • Proximity Sensors: Detect the proximity of an object without physical contact.
    • Pressure Sensors: Convert pressure to electrical signals.
    • IR (Infrared) Sensors: Detect infrared radiation.
    • Biosensors: Combine biological elements with transducers to detect analytes.

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