Electrical Measurements and Instrumentation MCQs (Part-6)
What does an analog voltmeter measure?
A Electric current
B Voltage
C Power
D Resistance
An analog voltmeter is designed to measure the potential difference (voltage) across two points in an electrical circuit.
Which of the following is used to measure the rotational speed of a machine?
A Oscilloscope
B Tachometer
C Wattmeter
D Thermistor
A tachometer is used to measure the rotational speed of machines, often in terms of revolutions per minute (RPM).
What is the function of an instrument transformer?
A To measure power directly
B To measure very high voltage or current safely
C To amplify electrical signals
D To reduce resistance
Instrument transformers, such as current transformers (CTs) and potential transformers (PTs), are used to step down high voltage or current to safer levels for measurement and protection.
Which instrument is used to measure the phase difference between two AC signals?
A Ammeter
B Phase meter
C Voltmeter
D Wattmeter
A phase meter measures the phase angle difference between two alternating current (AC) waveforms, providing insight into the synchronization of the signals.
What is the basic principle of an LVDT?
A Variation in capacitance
B Variation in inductance
C Piezoelectric effect
D Resistance change
An LVDT (Linear Variable Differential Transformer) works by detecting changes in inductance as a magnetic core moves within a set of coils, providing accurate displacement measurements.
Which type of error is caused by imperfections in instrument construction?
A Gross error
B Instrumental error
C Random error
D Environmental error
Instrumental errors are caused by design or manufacturing flaws in the instrument, which result in inaccurate readings.
What is the function of a dynamometer-type wattmeter?
A To measure energy directly
B To measure average power
C To measure instantaneous power
D To measure current
A dynamometer-type wattmeter measures the average power in AC or DC circuits using the interaction between fixed and moving coils to calculate power.
What does the term “sensitivity” of a measuring instrument mean?
A The ability to detect small changes in input
B The maximum value it can measure
C The ability to reduce noise
D The speed of measurement
Sensitivity refers to the smallest input change that can be detected by a measuring instrument, making it critical for accurate measurements in small variations.
Which type of noise can be minimized using low-pass filters?
A Thermal noise
B High-frequency noise
C Electromagnetic interference
D Shot noise
Low-pass filters are used to eliminate high-frequency noise by allowing lower frequencies to pass while blocking higher frequencies.
What is the primary function of a Wheatstone bridge?
A To measure resistance
B To measure capacitance
C To measure inductance
D To measure voltage
The Wheatstone bridge is used to measure unknown resistances by balancing two legs of a bridge circuit with known resistances.
What is the main purpose of a load cell?
A To measure temperature
B To measure weight or force
C To measure pressure
D To measure current
Load cells are force transducers that convert applied force into an electrical signal, commonly used for weighing applications.
Which property of a material is measured using a strain gauge?
A Electrical resistance
B Deformation (strain)
C Capacitance
D Thermal conductivity
Strain gauges measure the deformation (strain) in a material by detecting changes in electrical resistance caused by strain.
Which transducer operates on the piezoelectric principle?
A Thermocouple
B Piezoelectric sensor
C LVDT
D Strain gauge
Piezoelectric sensors generate an electrical voltage in response to mechanical stress based on the piezoelectric effect.
What type of error arises from human mistakes during measurement?
A Gross error
B Systematic error
C Random error
D Instrumental error
Gross errors are mistakes made during the measurement process, such as reading the instrument incorrectly or recording wrong data.
What is the main principle of a thermistor?
A Capacitance variation
B Resistance variation with temperature
C Magnetic field induction
D Piezoelectric effect
A thermistor’s resistance changes significantly with temperature, making it an excellent choice for temperature sensing applications.
What is the function of a frequency counter?
A To measure voltage
B To measure the frequency of an electrical signal
C To measure current
D To measure resistance
Frequency counters are used to measure the frequency of electrical signals, often displayed in Hertz (Hz), by counting the number of cycles in a given time period.
Which sensor is used for flow measurement?
A Strain gauge
B Venturi meter
C Tachometer
D Thermistor
A Venturi meter measures fluid flow by detecting pressure differences across a constriction in a pipe, with the pressure drop corresponding to the flow rate.
What is the purpose of calibration?
A To increase the sensitivity of an instrument
B To ensure accuracy by comparing with a standard
C To reduce noise in measurements
D To extend the range of measurement
Calibration is the process of adjusting an instrument to ensure its measurements are accurate by comparing them against a known standard.
Which type of transducer is used for pressure measurement?
A Capacitive transducer
B Thermocouple
C Tachometer
D Multimeter
Capacitive transducers are commonly used to measure pressure by detecting changes in capacitance when pressure is applied to a diaphragm that alters the distance between capacitor plates.
Which error type is minimized by proper shielding in electrical instruments?
A Random error
B Environmental error
C Instrumental error
D Gross error
Proper shielding in electrical instruments helps to reduce environmental errors, such as electromagnetic interference (EMI), which can affect the accuracy of measurements.