MEASUREMENT AND INSTRUMENTATION QUIZ

A spring-controlled moving iron voltmeter draws a current of 1 mA for full scale value of 100V. If it draws a current of 0.5 mA, the meter reading is

25 V.

100 V.

50 V.

200 V.

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YOUR ANSWER : ?

Which instrument has identical calibration for ac as well as dc values?

Moving iron type

Induction type

Moving coil type

Hot wire type

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In a moving iron meter, the deflecting torque is proportional to

Sine of the measurand

Square of the current through the coil

Squareroot of the measurand

Current through the coil

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The current coil of a wattmeter is connected to the CT of R-phase. The potential coil is connected across Y and B phases. The wattmeter measures

Active power in R phase

Reactive power of R phase

Active power of Y phase

Power proportional to 3 phase power if the load is balanced

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Comparison methods are used

when a high accuracy of measurement is required.

because they take least time in measurement.

because they are expensive.

because they are most simple.

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A thermometer having first order dynamics is subjected to a sudden temperature change of 30oc to 150oc. If it has he time constant of 5 sec, what temperature will be indicated by after 5 sec?

150o.

105.6o.

30o.

63.25o.

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It can be stated that

No generalisation can be made with regard to the flux densities in CT and PT

CT operates with considerably lower flux density than a PT

CT operates with a higher flux density than PT

CT operates at almost the same flux density as a PT

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In a portable instrument , the controlling torque is provided by

All of the listed here

Gravity

Spring

Eddy currents

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The rectifier instrument is not free from

Wave shape error

All of the listed here

Temperature error

Frequency error

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PMMC type instruments normally use

Eddy current damping

None of these

Air friction damping

Fluid friction damping

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