Measurement Errors and Accuracy - Electrical and Electronic Measurements - Electrical Engineering Previous Year Questions

1

2008 · Electrical Engineering · Electrical and Electronic Measurements · Measurement Errors and Accuracy

Electrical Engineering (EE) 2008

It is desired to measure parameters of 230 V / 115 V, 2 kVA, single-phase transformer. The following wattmeters are available in a laboratory: W1: 250 V, 10 A, Low Power Factor; W2: 250 V, 5 A, Low Power Factor; W3: 150 V, 10 A, High Power Factor; W4: 150 V, 5 A, High Power Factor. The wattmeters used in open circuit test and short circuit test of the transformer will respectively be

A

W1 and W3

B

W2 and W4

C

W1 and W4

D

W2 and W3

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2

2009 · Electrical Engineering · Electrical and Electronic Measurements · Measurement Errors and Accuracy

Electrical Engineering (EE) 2009

The measurement system shown in the figure uses three sub-systems in cascade whose gains are specified as \(G_1\), \(G_2\) and \(\frac{1}{G_3}\). The relative small errors associated with each respective subsystem \(G_1\), \(G_2\) and \(G_3\) are \(\varepsilon_1\), \(\varepsilon_2\) and \(\varepsilon_3\). The error associated with the output is:

A

\(\varepsilon_1 + \varepsilon_2 + \frac{1}{\varepsilon_3}\)

B

\(\frac{\varepsilon_1 \cdot \varepsilon_2}{\varepsilon_3}\)

C

\(\varepsilon_1 + \varepsilon_2 - \varepsilon_3\)

D

\(\varepsilon_1 + \varepsilon_2 + \varepsilon_3\)

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3

2009 · Electrical Engineering · Electrical and Electronic Measurements · Measurement Errors and Accuracy

Electrical Engineering (EE) 2009

An average-reading digital multimeter reads 10V when fed with a triangular wave, symmetric about the time-axis. For the same input an rms-reading meter will read

A

20/√3

B

10/√3

C

20√3

D

10√3

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4

2011 · Electrical Engineering · Electrical and Electronic Measurements · Measurement Errors and Accuracy

Electrical Engineering (EE) 2011

A lossy capacitor C_X, rated for operation at 5 kV, 50 Hz is represented by an equivalent circuit with an ideal capacitor C_P in parallel with a resistor R_P. The value of C_P is found to be 0.102 μF and the value of R_P = 1.25 MΩ. Then the power loss and tan δ of the lossy capacitor operating at the rated voltage, respectively, are

A

10 W and 0.0002

B

10 W and 0.0025

C

20 W and 0.025

D

20 W and 0.04

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5

2011 · Electrical Engineering · Electrical and Electronic Measurements · Measurement Errors and Accuracy

Electrical Engineering (EE) 2011

A 4½ digit DMM has the error specification as : 0.2 % of reading + 10 counts. If a dc voltage of 100 V is read on its 200 V full scale, the maximum error that can be expected in the reading is

A

±0.1 %

B

±0.2 %

C

±0.3 %

D

±0.4 %

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6

2012 · Electrical Engineering · Electrical and Electronic Measurements · Measurement Errors and Accuracy

Electrical Engineering (EE) 2012

An analog voltmeter uses external multiplier settings. With a multiplier setting of 20 kΩ, it reads 440 V and with a multiplier setting of 80 kΩ, it reads 352 V. For a multiplier setting of 40 kΩ, the voltmeter reads

A

371 V

B

383 V

C

394 V

D

406 V

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7

2013 · Electrical Engineering · Electrical and Electronic Measurements · Measurement Errors and Accuracy

Electrical Engineering (EE) 2013 [Session 1]

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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8

2014 · Electrical Engineering · Electrical and Electronic Measurements · Measurement Errors and Accuracy

Electrical Engineering (EE) 2014 [Session 1]

The undesirable property of an electrical insulating material is

A

high dielectric strength

B

high relative permittivity

C

high thermal conductivity

D

high insulation resistivity

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9

2014 · Electrical Engineering · Electrical and Electronic Measurements · Measurement Errors and Accuracy

Electrical Engineering (EE) 2014 [Session 1]

The dc current flowing in a circuit is measured by two ammeters, one PMMC and another electrodynamometer type, connected in series. The PMMC meter contains 100 turns in the coil, the flux density in the air gap is 0.2 Wb/m², and the area of the coil is 80 mm². The electrodynamometer ammeter has a change in mutual inductance with respect to deflection of 0.5 mH/deg. The spring constants of both the meters are equal. The value of current, at which the deflections of the two meters are same, is ______.

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10

2014 · Electrical Engineering · Electrical and Electronic Measurements · Measurement Errors and Accuracy

Electrical Engineering (EE) 2014 [Session 2]

Two ammeters X and Y have resistances of 1.2 Ω and 1.5 Ω respectively and they give full-scale deflection with 150 mA and 250 mA respectively. The ranges have been extended by connecting shunts so as to give full scale deflection with 15 A. The ammeters along with shunts are connected in parallel and then placed in a circuit in which the total current flowing is 15A. The current in amperes indicated in ammeter X is __________.

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11

2014 · Electrical Engineering · Electrical and Electronic Measurements · Measurement Errors and Accuracy

Electrical Engineering (EE) 2014 [Session 3]

A periodic waveform observed across a load is represented by
\[ V(t) = \begin{cases} 1 + \sin \omega t & 0 \le \omega t < 6\pi \\ -1 + \sin \omega t & 6\pi \le \omega t < 12\pi \end{cases} \]
The measured value, using moving iron voltmeter connected across the load, is

A

\(\sqrt{\frac{3}{2}} \)

B

\(\sqrt{\frac{2}{3}} \)

C

3/2

D

2/3

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12

2016 · Electrical Engineering · Electrical and Electronic Measurements · Measurement Errors and Accuracy

Electrical Engineering (EE) 2016 [Session 1]

A dc voltage with ripple is given by \(v(t) = [100 + 10 \sin(\omega t) - 5 \sin(3\omega t)]\) volts. Measurements of this voltage \(v(t)\), made by moving-coil and moving-iron voltmeters, show readings of \(V_1\) and \(V_2\) respectively. The value of \(V_2 - V_1\), in volts, is ________.

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13

2016 · Electrical Engineering · Electrical and Electronic Measurements · Measurement Errors and Accuracy

Electrical Engineering (EE) 2016 [Session 1]

A temperature in the range of \(-40^{\circ} C\) to \(55^{\circ} C\) is to be measured with a resolution of \(0.1^{\circ} C\). The minimum number of ADC bits required to get a matching dynamic range of the temperature sensor is

A

8

B

10

C

12

D

14

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14

2016 · Electrical Engineering · Electrical and Electronic Measurements · Measurement Errors and Accuracy

Electrical Engineering (EE) 2016 [Session 2]

An energy meter, having meter constant of 1200 revolutions/kWh, makes 20 revolutions in 30 seconds for a constant load. The load, in kW, is __________.

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15

2017 · Electrical Engineering · Electrical and Electronic Measurements · Measurement Errors and Accuracy

Electrical Engineering (EE) 2017 [Session 1]

The following measurements are obtained on a single phase load: V = 220 V \(\pm\) 1 %, I = 5.0 A \(\pm\) 1% and W = 555 W \(\pm\) 2 %. If the power factor is calculated using these measurements, the worst case error in the calculated power factor in percent is ________. (Give answer up to one decimal place.)

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16

2017 · Electrical Engineering · Electrical and Electronic Measurements · Measurement Errors and Accuracy

Electrical Engineering (EE) 2017 [Session 1]

The load shown in the figure is supplied by a 400 V (line-to-line), 3-phase source (RYB sequence). The load is balanced and inductive, drawing 3464 VA. When the switch S is in position N, the three watt-meters W1, W2 and W3 read 577.35 W each. If the switch is moved to position Y, the readings of the watt-meters in watts will be:

A

\(W_1 = 1732 \) and \(W_2 = W_3 = 0 \)

B

\(W_1 = 0, W_2 = 1732 \) and \(W_3 = 0 \)

C

\(W_1 = W_2 = 0 \) and \(W_3 = 1732 \)

D

\(W_1 = W_2 = W_3 = 577.35 \)

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17

2017 · Electrical Engineering · Electrical and Electronic Measurements · Measurement Errors and Accuracy

Electrical Engineering (EE) 2017 [Session 2]

Two resistors with nominal resistance values \(R_1\) and \(R_2\) have additive uncertainties \(\Delta R_1\) and \(\Delta R_2\), respectively. When these resistances are connected in parallel, the standard deviation of the error in the equivalent resistance \(R\) is

A

\(\pm \sqrt{\left(\frac{\partial R}{\partial R_1} \Delta R_1\right)^2 + \left(\frac{\partial R}{\partial R_2} \Delta R_2\right)^2}\)

B

\(\pm \sqrt{\left(\frac{\partial R}{\partial R_2} \Delta R_1\right)^2 + \left(\frac{\partial R}{\partial R_1} \Delta R_2\right)^2}\)

C

\(\pm \sqrt{\left(\frac{\partial R}{\partial R_1}\right)^2 \Delta R_2 + \left(\frac{\partial R}{\partial R_2}\right)^2 \Delta R_1}\)

D

\(\pm \sqrt{\left(\frac{\partial R}{\partial R_1}\right)^2 \Delta R_1 + \left(\frac{\partial R}{\partial R_2}\right)^2 \Delta R_2}\)

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18

2018 · Electrical Engineering · Electrical and Electronic Measurements · Measurement Errors and Accuracy

Electrical Engineering (EE) 2018

A 0-1 Ampere moving iron ammeter has an internal resistance of 50 m\(\Omega\) and inductance of 0.1 mH. A shunt coil is connected to extend its range to 0-10 Ampere for all operating frequencies. The time constant in milliseconds and resistance in m\(\Omega\) of the shunt coil respectively are

A

2, 5.55

B

2, 1

C

2.18, 0.55

D

11.1, 2

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19

2020 · Electrical Engineering · Electrical and Electronic Measurements · Measurement Errors and Accuracy

Electrical Engineering (EE) 2020

A non-ideal Si-based pn junction diode is tested by sweeping the bias applied across its terminals from −5 V to +5 V. The effective thermal voltage, \(V_T\), for the diode is measured to be (29 ± 2) mV. The resolution of the voltage source in the measurement range is 1 mV. The percentage uncertainty (rounded off to 2 decimal places) in the measured current at a bias voltage of 0.02 V is ____________.

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20

2020 · Electrical Engineering · Electrical and Electronic Measurements · Measurement Errors and Accuracy

Electrical Engineering (EE) 2020

The temperature of the coolant oil bath for a transformer is monitored using the circuit shown. It contains a thermistor with a temperature-dependent resistance, \(R_{thermistor} = 2 (1 + \alpha T)\) kΩ, where \(T\) is the temperature in °C. The temperature coefficient, \(\alpha\), is \(-(4 \pm 0.25)\) %/°C. Circuit parameters: \(R_1 = 1\) kΩ, \(R_2 = 1.3\) kΩ, \(R_3 = 2.6\) kΩ. The error in the output signal (in V, rounded off to 2 decimal places) at 150°C is ________.

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