Basic of Indicating Instruments · Electrical and Electronics Measurement · GATE EE

Two balanced three-phase loads, as shown in the figure, are connected to a $$100\sqrt 3 $$ V, three-phase, 50 Hz main supply. Given Z₁ = (18 + j24) $$\Omega$$ and Z₂ = (6 + j8) $$\Omega$$. The ammeter reading, in amperes, is _________. (round off to nearest integer).

A ($$0-50$$ $$A$$) moving coil ammeter has a voltage drop of $$0.1$$ $$V$$ across its terminals at full scale deflection. The external shunt resistance (in $$milliohms$$) needed to extend its range to ($$0 – 500$$ $$A$$) is ______.

Match the following.

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

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

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 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

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

A $$PMMC$$ voltmeter is connected across a series combination of a $$DC$$ voltage source $${V_1} = 2V$$ and $$AC$$ voltage source $${V_2}\left( t \right) = 3$$ $$sin(4t)$$ $$V.$$ The meter reads

A galvanometer with a full scale current of $$10$$ $$mA$$ has a resistance of $$1000$$$$\Omega $$. The multiplying power (the ratio of measured current to galvanometer current) of a $$100$$$$\Omega $$ shunt with this galvanometer is

The effect of stray magnetic fields on the actuating torque of a portable instrument is maximum when the operating field of the instrument and the stray fields are

A Manganin swamping resistance is connected in series with a moving coil ammeter consisting of a milli-ammeter and a suitable shunt in order to

A d.c. voltmeter has a sensitivity of $$1000$$$$\Omega /volt.$$ When it measures half full scale in $$100$$ $$V$$ range, the current through the voltmeter is

A moving coil galvanometer is made into a d.c. ammeter by connecting

An advantage of a permanent magnet moving coil instrument is that it is

The scale of a voltmeter is uniform. Its type is

For a given frequency, the deflecting torque of an induction ammeter is directly proportional to

Four ammeters $$M1, M2, M3$$ and $$M4$$ with the following specifications are available.

A current of $$1$$ $$A$$ is to be measured. To obtain minimum error in the reading, one should select meter

Two $$100V$$ full scale $$PMMC$$ type D.C voltmeter having figure of merits ($$FOM)$$ of $$10k\Omega /V$$ and $$20k\Omega /V$$ are connected in series. The series combination can be used to measure a maximum dc voltage of _______.

A $$0$$-$$10$$ $$mA$$ $$PMMC$$ ammeter reads $$4$$ $$mA$$ in a circuit. Its bottom control spring snaps suddenly. The meter will now read nearly

An unshielded moving iron voltmeter is used to measure the voltage in an a.c. circuit. If a stray d.c. magnetic field having a component along the axis of the meter coil appears, the meter reading would be

The current $$i(t)$$ passing through $$10\Omega $$ resistor as shown in fig $$A$$. as a waveform as shown in fig $$B.$$ Then the reading of the d.c voltmeter is connected across $$10\Omega $$ resistor is

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 dc voltage with ripple is given by $$v\left( t \right)\,\,\,\, = \,\,\,\,\left[ {100 + 10\sin \left( {\omega t} \right) - 5\sin \left( {3\omega t} \right)} \right]$$ volts. Measurements of this voltage $$v\left( t \right),$$ 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 _______.

Two ammeters $$X$$ and $$Y$$ have resistances of $$1.2$$ $$\Omega $$ and $$1.5$$ $$\Omega $$ 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 __________.

A periodic waveform observed across a load is represented by $$$V\left( t \right) = \left\{ {\matrix{ {1 + \sin \,\omega t} & {0 \le \omega t < 6\pi } \cr { - 1 + \sin \,\omega t} & {6\pi \le \omega t < 12\pi } \cr } } \right.$$$
$$6\pi \le \omega t < 12\,\pi $$
The measured value, using moving iron voltmeter connected across the load, is

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, it which the deflection of the two meters are same, is ___________.

The reading of voltmeter $$(rms)$$ in volts, for the circuit shown in the figure is ______.

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

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 current of $$ - 8 + 6\sqrt 2 \left( {\sin \,\omega t + {{30}^0}} \right)\,\,A$$ is passed though three meters. They are a center zero $$PMMC$$ meter, true $$r.m.s$$ meter and moving $${\rm I}$$ron instrument. The respective reading (in $$A$$) will be

A $$1000$$ $$V$$ $$DC$$ supply has two $$1-core$$ cables as its positive and negative leads: their insulation resistances to earth are $$4\,\,M\Omega $$ and $$6\,\,M\Omega $$, respectively, as shown in figure. A voltmeter with resistance $$50\,\,k\Omega $$ is used to measure the insulation of the cable. When connected between the positive core and earth, the voltmeter reads

A DC ammeter has a resistance of $$0.1$$$$\Omega $$ and its current range is $$0$$ – $$100A.$$ If the range is to be extended to $$0$$ –$$500A,$$ the meter requires the following shunt resistance

A moving coil of a meter has $$100$$ turns, and a length and depth of $$10$$ $$mm$$ and $$20$$ $$mm$$ respectively. It is positioned in a uniform radial flux density of $$200$$ $$mT.$$ The coil carries a current of $$50$$ $$mA.$$ The torque on the coil is

A moving iron ammeter produces a full scale torque of $$240$$ $$\,\mu Nm$$ with a deflection of $${120^ \circ }$$ at a current of $$10$$ $$A$$. The rate of change of self inductance $$\left( {\mu H/radian} \right)$$ of the instrument at full scale is

The inductance of a certain moving-iron ammeter is expressed as $$L = 10 + 3\theta - {{{\theta ^2}} \over 4}\mu H,\,\,$$ where $$\,\,\theta \,\,\,$$ is the deflection in radians from the zero position. The control spring torque in $$\,\,25\,\, \times \,\,{10^{ - 6}}\,\,\,$$ Nm/radian. The deflection of the pointer in radian when the meter carries a current of $$5A,$$ is

An ac voltmeter uses the circuit shown below, where the $$PMMC$$ meter has an internal resistance of $$100$$$$\Omega $$ and requires a dc current of $$1$$ $$mA$$ for full scale deflection. Assuming the diodes to be ideal, the value of $${R_s}$$ to obtain full scale deflection with $$100$$ $$V$$ (ac rms) applied to the input terminal would be

A $$100$$ $$\mu A$$ ammeter has an internal resistance of $$100\,\Omega $$. For extending its range to measure $$500$$ $$\mu A$$, the shunt required is of resistance (in $$\Omega $$)

A current of $$\left[ {2 + \sqrt 2 \sin \left( {314t + 30} \right) + 2\sqrt 2 \cos \left( {952t + 45} \right)} \right]$$ is measured with a thermocouple type. $$5A$$ full scale, class $$1$$ meter. The meter reading would like in the range,

For the given circuit the internal resistance of the ammeters as well as that of the current coil of the wattmeter are zero, and the voltmeters have a very large figure of merit. $${A_1}$$ is a $$6A$$ full scale moving $${\rm I}$$ron type meter. $${A_2}$$ is a commercial full wave rectifier type meter of full scale $$5A$$. $${V_1}$$ is a $$500V$$ meter is an peak response type. $${V_2}$$ is a $$300V$$ $$PMMC$$ type meter and $$W$$ is an electro dynamometer type, $$5A$$, $$230V$$ wattmeter. Determine the readings of $${A_1},$$ $${A_2},$$ $${V_1},$$ $${V_2},$$ and $$W.$$