# Recent questions and answers in Electrical Measurements and Instrumentation

What type of meter is used to measure current?

A VTVM can be used to measure (a) dc voltage only (b) ac voltage only (c) both (a) and (b) (d) None of the above

A digital voltmeter has a read-out range from 0 to 9999 counts. When full scale reading is 9.999 V, the resolution of the instrument will be (a) 100 mV (b) 99 mV (c) 9 mV (d) 1 mV

What equipment is used to measure voltage?

Eddy current damping is normally used in the instruments of (a) Induction type (b) Moving iron type (c) Permanent magnet moving coil type (d) Nothing can be said

Hot wire ammeter is used (a) only for dc circuit (b) only for ac circuit (c) both (a) and (b) (d) Either (a) or (b)

Permanent magnet moving coil instruments are used for

The Maxwell bridge is used for measuring (a) Capacitance (b) Dielectric loss (c) Inductance (d) Phase angle

A Wien bridge is used to measure (A) quality factor of a coil (B) audio frequency of a signal (C) capacitance of a capacitor (D) inductance of a coil

The bridge used to measure the dielectric loss of an insulator is: A) Anderson bridge B) Wien’s bridge C) Schering bridge D) Any of the above

Megger is used to measure (a) very high resistance or insulation resistance. (b) low resistance. (c) high resistance. (d) very low resistance.

Digital meters are superior over analogue meters because (A) less expensive (B) output reading is binary in nature (C) output impedance is less (D) installation is easy as panel meters

Which of the following instruments can be used for measurement of very high value resistances such as insulation resistance in industries? A) Wheatstone bridge B) Megger C) Ohm-meter D) Resistive potentiometer

A 10A DC Ammeter has a resistance of 0.1 Ω is to be extended to 50 A, the required shunt wire is A) Manganin wire of 20 m Ω B) Constantan wire of 20 m Ω C) Manganin wire of 25 m Ω D) Constantan wire of 25 m Ω

Two stator windings of AC servomotors are oriented: A) 90 degree (mechanical) apart B) 90 degree (electrical) apart C) 180 degree (mechanical) apart D) 180 degree (electrical) apart

Highest flux density exists inside which of the following instruments? A) Electrodynamic instruments B) Hot wire instruments C) Moving iron instruments D) Moving coil instruments

In the measurement of power of balanced load by two wattmeter method in a 3-phase circuit, The readings of the wattmeters are 4 kW and 2 kW respectively, the later is being taken after reversing the connections of current coil. the power factor and reactive power of the load is A) 0.2 & 6 kVAR B) 0.2 & 6 √3 kVAR C) 0.32 & 2 kVAR D) 0.32 & 2 √3 kVAR

The full scale range of PMMC voltmeter is 100 V and its sensitivity is 1000 Ω/V. If the meter reads 50 V, the current through the voltmeter is (A) 0.05 mA (B) 0.5 mA (C) 5 mA (D) 50 mA

The power in a 3-phase load is measured by two watt meters. If one watt meter reads zero, then the load power factor is (A) Zero (B) 0.5 (C ) 0.866 (D) unity

The burden of the instrument transformers is (A) VA rating (B) secondary winding current (C) secondary winding voltage (D) (secondary winding current)2 × resistance of secondary winding

The most accurate instrument for measuring phase difference between two signals is (A) X− Y plotter (B) oscilloscope (C) phase sensitive detector (D) electronic counter/timer

Measurement of power by voltmeter and ammeter method in a circuit resulted in calculated maximum errors of ±1 % and ± 2 %, respectively. The likely error in calculated power is (A) ± 3 % (B) ± 0.022 % (C) ± 1.5 % (D) ± 0.22 %

In a standard multimeter for measuring AC voltage, parameter of _____ voltage is measured

In dynamometer type of wattmeter, which of the coil is split up into two parts?

Moire fringes are used to measure rotary displacement along with _____.

The function of measurement system is/are _____.

A 0-10 A ammeter has a guaranteed accuracy of 1% of full scale deflection, the limiting error while reading 2.5 A will be (a) 1% (b) 2% (c) 4% (d) None of these

The constant of a given energy meter is 500 revolution/kWh. At the test 4.4 kW full load, meter completes 50 revolutions in 86 seconds. The percentage error of the meter is (a) –4.86% (b) 4.86% (c) 2.0% (d) 3.0%

Which of the following instruments is equally accurate on ac as well as dc circuits ? (a) PMMC voltmeter (b) Dynamometer wattmeter (c) Moving iron ammeter (d) Induction wattmeter

The moving system of an indicating type of electrical instrument is subjected to (a) a deflecting torque (b) a controlling torque (c) a damping torque (d) All of the above

Energy meter runs slowly even if power is not used. This error is called (a) Speed error (b) Phase error (c) Creeping error (d) None of these

The type of instruments used mainly for standardizing instruments in laboratories is (a) Indicating instrument (b) Integrating instrument (c) Absolute instrument (d) Recording instrument

What will happen if a voltmeter is connected like an ammeter in series of the load ? (a) The meter will burn out. (b) The measurement will be too high. (c) The same current will flow as would have been with ammeter in circuit. (d) There will be almost no current in the circuit.

Series resistance required to read 0-250 V with a moving coil instrument of internal resistance 2 ohm and full scale deflection of 50 mA is (a) 49998 Ω (b) 4998 Ω (c) 498 Ω (d) 49.8 Ω

Which of the following is not a method of resistance measurement ? (a) Ammeter – Voltmeter method (b) Post – Office box method (c) Ohm – Meter method (d) Two wattmeter method

Internal resistance of a micro-ammeter is 500 ohm. Shunt resistance required to increase its range from 0-100 µA to 0-10 A will be approximately (a) 0.05 Ω (b) 0.005 Ω (c) 0.5 Ω (d) 5.0 Ω

Hay bridge is suitable for measuring following type of inductance (a) having Q greater than 10. (b) having Q less than 10. (c) having any value of Q. (d) having phase angle of reactance very large.

In a particular meter, the deflecting torque is directly proportional to the current flowing through it, the type of meter is (a) moving coil (b) moving iron (c) induction (d) electro-static

For measurement of low resistance, the bridge used is (a) Wheatstone (b) Kelvin (c) Maxwell (d) Anderson

While measuring power in a three phase load by two wattmeter method, the reading of two wattmeter are equal and opposite, when (a) load is balanced (b) power factor is unity (c) phase angle is between 60° to 90° (d) the load is purely inductive

If a dynamometer wattmeter is connected in an ac circuit, the power indicated by the wattmeter will be (a) volt-ampere product (b) average power (c) peak power (d) instantaneous power

A compensated wattmeter has its reading corrected for error due to (a) Frequency (b) Friction (c) Power consumed in current coil (d) Power consumed in pressure coil

A null type of instrument as compared to a deflecting type instrument has (a) higher accuracy (b) lower sensitivity (c) faster response (d) All of the above

The sensitivity of a voltmeter using 0-5 mA meter movement is (a) 200 Ω/V (b) 150 Ω/V (c) 100 Ω/V (d) 50 Ω/V

The disc of domestic supply energy meter is made of which material ? (a) Zinc (b) Copper (c) Aluminium (d) Silver