Instrument Transformers and Digital Instruments - Electrical and Electronic Measurements - Electrical Engineering Previous Year Questions

1

2007 · Electrical Engineering · Electrical and Electronic Measurements · Instrument Transformers and Digital Instruments

Electrical Engineering (EE) 2007

The probes of a non-isolated, two-channel oscilloscope are clipped to points A, B and C in the circuit of the adjacent figure. \(V_{in}\) is a square wave of a suitable low frequency. The display on \(Ch_1\) and \(Ch_2\) are as shown on the right. Then the "Signal" and "Ground" probes \(S_1\), \(G_1\) and \(S_2\), \(G_2\) of \(Ch_1\) and \(Ch_2\) respectively are connected to points:

A

A, B, C, A

B

A, B, C, B

C

C, B, A, B

D

B, A, B, C

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2

2008 · Electrical Engineering · Electrical and Electronic Measurements · Instrument Transformers and Digital Instruments

Electrical Engineering (EE) 2008

Two 8-bit ADCs, one of single slope integrating type and other of successive approximation type, take $T_A$ and $T_B$ times to convert 5 V analog input signal to equivalent digital output. If the input analog signal is reduced to 2.5V, the approximate time taken by the two ADCs will respectively, be

A

$T_A, T_B$

B

$T_A/2, T_B$

C

$T_A, T_B/2$

D

$T_A/2, T_B/2$

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3

2008 · Electrical Engineering · Electrical and Electronic Measurements · Instrument Transformers and Digital Instruments

Electrical Engineering (EE) 2008

Two sinusoidal signals p(ωt) = A sin ωt and q(ωt) are applied to X and Y inputs of a dual channel CRO. The Lissajous figure displayed on the screen is shown below:

The signal q(ω₂t) will be represented as

A

q(ω₂t) = A sin ω₂t, ω₂ = 2ω₁

B

q(ω₂t) = A sin ω₂t, ω₂ = ω₁/2

C

q(ω₂t) = A cos ω₂t, ω₂ = 2ω₁

D

q(ω₂t) = A cos ω₂t, ω₂ = ω₁/2

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4

2009 · Electrical Engineering · Electrical and Electronic Measurements · Instrument Transformers and Digital Instruments

Electrical Engineering (EE) 2009

The two inputs of a CRO are fed with two stationary periodic signals. In the X-Y mode, the screen shows a figure which changes from ellipse to circle and back to ellipse with its major axis changing orientation slowly and repeatedly. The following inference can be made from this.

A

The signals are not sinusoidal

B

The amplitudes of the signals are very close but not equal

C

The signals are sinusoidal with their frequencies very close but not equal

D

There is a constant but small phase difference between the signals

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5

2010 · Electrical Engineering · Electrical and Electronic Measurements · Instrument Transformers and Digital Instruments

Electrical Engineering (EE) 2010

An ammeter has a current range of 0 – 5 A, and its internal resistance is 0.2 Ω. In order to change the range to 0 – 25 A, we need to add a resistance of

A

0.8 Ω in series with the meter.

B

1.0 Ω in series with the meter.

C

0.04 Ω in parallel with the meter.

D

0.05 Ω in parallel with the meter.

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6

2011 · Electrical Engineering · Electrical and Electronic Measurements · Instrument Transformers and Digital Instruments

Electrical Engineering (EE) 2011

A dual trace oscilloscope is set to operate in the ALTERNATE mode. The control input of the multiplexer used in the y-circuit is fed with a signal having a frequency equal to

A

the highest frequency that the multiplexer can operate properly

B

twice the frequency of the time base (sweep) oscillator

C

the frequency of the time base (sweep) oscillator

D

half the frequency of the time base (sweep) oscillator

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7

2012 · Electrical Engineering · Electrical and Electronic Measurements · Instrument Transformers and Digital Instruments

Electrical Engineering (EE) 2012

A periodic voltage waveform observed on an oscilloscope across a load is shown. A permanent magnet moving coil (PMMC) meter connected across the same load reads

A

4 V

B

5 V

C

8 V

D

10 V

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8

2013 · Electrical Engineering · Electrical and Electronic Measurements · Instrument Transformers and Digital Instruments

Electrical Engineering (EE) 2013 [Session 3]

Three moving iron type voltmeters are connected as shown below. Voltmeter readings are \( V \), \( V_1 \) and \( V_2 \), as indicated. The correct relation among the voltmeter readings is

A

\(V = \frac{V_1}{\sqrt{2}} + \frac{V_2}{\sqrt{2}} \)

B

\(V = V_1 + V_2 \)

C

\(V = V_1 V_2 \)

D

\(V = V_2 - V_1 \)

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9

2013 · Electrical Engineering · Electrical and Electronic Measurements · Instrument Transformers and Digital Instruments

Electrical Engineering (EE) 2013 [Session 3]

The input impedance of the permanent magnet moving coil (PMMC) voltmeter is infinite. Assuming that the diode shown in the figure below is ideal, the reading of the voltmeter in Volts is

A

4.46

B

3.15

C

2.23

D

0

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10

2013 · Electrical Engineering · Electrical and Electronic Measurements · Instrument Transformers and Digital Instruments

Electrical Engineering (EE) 2013 [Session 4]

Three moving iron type voltmeters are connected as shown below. Voltmeter readings are \( V, V_1 \) and \( V_2 \), as indicated. The correct relation among the voltmeter readings is

A

\(V = \frac{V_1}{\sqrt{2}} + \frac{V_2}{\sqrt{2}} \)

B

\(V = V_1 + V_2 \)

C

\(V = V_1 V_2 \)

D

\(V = V_2 - V_1 \)

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11

2014 · Electrical Engineering · Electrical and Electronic Measurements · Instrument Transformers and Digital Instruments

Electrical Engineering (EE) 2014 [Session 1]

In an oscilloscope screen, linear sweep is applied at the

A

vertical axis

B

horizontal axis

C

origin

D

both horizontal and vertical axis

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12

2014 · Electrical Engineering · Electrical and Electronic Measurements · Instrument Transformers and Digital Instruments

Electrical Engineering (EE) 2014 [Session 2]

The saw-tooth voltage waveform shown in the figure is fed to a moving iron voltmeter. Its reading would be close to ______

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13

2017 · Electrical Engineering · Electrical and Electronic Measurements · Instrument Transformers and Digital Instruments

Electrical Engineering (EE) 2017 [Session 1]

The slope and level detector circuit in a CRO has a delay of 100 ns. The start-stop sweep generator has a response time of 50 ns. In order to display correctly, a delay line of

A

150 ns has to be inserted into the y-channel

B

150 ns has to be inserted into the x-channel

C

150 ns has to be inserted into both x and y channels

D

100 ns has to be inserted into both x and y channels

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14

2017 · Electrical Engineering · Electrical and Electronic Measurements · Instrument Transformers and Digital Instruments

Electrical Engineering (EE) 2017 [Session 2]

A stationary closed Lissajous pattern on an oscilloscope has 3 horizontal tangencies and 2 vertical tangencies for a horizontal input with frequency 3 kHz. The frequency of the vertical input is

A

1.5 kHz

B

2 kHz

C

3 kHz

D

4.5 kHz

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15

2017 · Electrical Engineering · Electrical and Electronic Measurements · Instrument Transformers and Digital Instruments

Electrical Engineering (EE) 2017 [Session 2]

A 10 ½ digit timer counter possesses a base clock of frequency 100 MHz. When measuring a particular input, the reading obtained is the same in: (i) Frequency mode of operation with a gating time of one second and (ii) Period mode of operation (in the x 10 ns scale). The frequency of the unknown input (reading obtained) in Hz is __________.

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16

2019 · Electrical Engineering · Electrical and Electronic Measurements · Instrument Transformers and Digital Instruments

Electrical Engineering (EE) 2019

The total impedance of the secondary winding, leads, and burden of a 5 A CT is 0.01 Ω. If the fault current is 20 times the rated primary current of the CT, the VA output of the CT is __________.

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17

2019 · Electrical Engineering · Electrical and Electronic Measurements · Instrument Transformers and Digital Instruments

Electrical Engineering (EE) 2019

A moving coil instrument having a resistance of \(10\ \Omega\), gives a full-scale deflection when the current is 10 mA. What should be the value of the series resistance, so that it can be used as a voltmeter for measuring potential difference up to 100 V?

A

\(9\ \Omega\)

B

\(99\ \Omega\)

C

\(990\ \Omega\)

D

\(9990\ \Omega\)

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18

2020 · Electrical Engineering · Electrical and Electronic Measurements · Instrument Transformers and Digital Instruments

Electrical Engineering (EE) 2020

Currents through ammeters A2 and A3 in the figure are \(1\angle10^\circ\) and \(1\angle70^\circ\), respectively. The reading of the ammeter A1(rounded off to 3 decimal places) is ______ A.

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19

2024 · Electrical Engineering · Electrical and Electronic Measurements · Instrument Transformers and Digital Instruments

Electrical Engineering (EE) 2024

The table lists two instrument transformers and their features:

Instrument Transformers	Features
	P) Primary is connected in parallel to the grid
X) Current Transformer (CT)	Q) Open circuited secondary is not desirable
Y) Potential Transformer (PT)	R) Primary current is the line current
	S) Secondary burden affects the primary current

The correct matching of the two columns is

A

X matches with P and Q; Y matches with R and S.

B

X matches with P and R; Y matches with Q and S.

C

X matches with Q and R; Y matches with P and S.

D

X matches with Q and S; Y matches with P and R.

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