Principles and Operation of Deflection-Type Meters

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One. What is the basic principle of operation of deflection-type meters?

Deflection-type meters operate on the principle that a mechanical force is created by the quantity being measured, such as current or voltage. This force acts upon a movable element, causing it to displace from its zero position. The movement is typically opposed by a controlling force, such as a spring, which ensures the deflection is proportional to the magnitude of the measured quantity. Once the deflecting torque and controlling torque balance out, the pointer comes to rest at a specific point on a calibrated scale. This allows the user to read the value of the electrical parameter directly.

Two. What is the relevance of controlling torque in such meters and how is this attained?

Controlling torque is essential because, without it, the pointer would move to the maximum position regardless of the magnitude of the measured quantity. It serves to oppose the deflecting torque and ensures that the deflection of the pointer is limited and proportional to the input signal. This torque also brings the moving system and pointer back to the zero position once the measurement is removed. It is typically attained using gravity control or spring control, with hairsprings made of phosphorous-bronze being the most common method.

Three. What do you mean by grounding? Explain, citing an example.

Four. Explain the significance of damping in deflection-type instruments.

Five. Write a short note on the sources and detectors used in the a.c. bridge.

Six. Illustrate an electrodynamic instrument.

Seven. List the disadvantages of a moving iron meter.

Eight. What is the working principle of a deflection-type indicating instrument?

Nine. Explain the construction and working of a D'Arsonval Galvanometer.

Ten. Differentiate between moving iron and moving coil instruments.

Eleven. Why are moving coil instruments not used for AC measurements?

Twelve. What is the function of damping in indicating instruments?

Thirteen. A zero to ten ampere moving coil ammeter has a resistance of twelve. What shunt resistance is required to measure up to fifty amperes?

Fourteen. How are instrument transformers used for protection and metering in high-voltage systems?

Fifteen. Describe how current probes measure DC current in a live wire.

Sixteen. Explain the necessity of shielding in a measurement system with an example.

Seventeen. How does improper grounding affect instrument accuracy and

Eighteen. Draw and label the internal structure of a moving coil instrument.

Nineteen. What are the essential components of an indicating instrument? Briefly explain each.

Twenty. Describe the principle of operation of a deflection-type instrument.

Twenty-one. What is the difference between controlling torque and deflecting torque in measuring instruments?

Twenty-two. Compare and contrast attraction and repulsion types of moving iron instruments.

Twenty-three. What are the limitations of moving iron instruments in AC measurements?

Twenty-four. What are deflection-type meters, and how do they differ from other types of measuring instruments?

Twenty-five. What is the principle behind the operation of electrostatic instruments?

Twenty-six. Explain the principle of operation for induction type instruments.

Twenty-seven. Why is damping necessary in an indicating instrument? What are the types of damping used?

Twenty-nine. What are the applications of the current transformers?

Thirty. Describe the construction and working principle of a moving coil instrument.

Thirty-one. What are the applications of the potential transformers?

Thirty-two. Explain the method used in moving iron instruments to achieve calibration and accurate measurements.

Thirty-four. Explain the method used in dynamometer instruments to achieve calibration and accurate measurements.

Thirty-six. Explain why the PMMC instruments are the most widely used instruments. Discuss their advantages and disadvantages.

Thirty-seven. List the advantages of PMMC meters.

Thirty-eight. List the errors in PMMC meters.

Thirty-nine. Explain the working of repulsion type of moving iron instruments with the help of a neat diagram.

Forty. Describe the methods of producing controlling and damping torques in moving iron instruments.

Forty-one. Explain the working of an attraction type moving iron instrument with the help of a diagram.

Forty-two. Explain why the electrodynamometer instruments can be used both for AC and DC?

Forty-three. Why are these instruments used as transfer instruments?

Forty-four. Write a note on the grounding and shielding practices in measurement systems.

Forty-five. What do you mean by shielding? Explain, with an example.

Forty-six. How is the range of D.C. Ammeter and D.C. voltmeter extended?

Forty-seven. Derive the expressions to calculate shunt resistance and multiplier resistance.

Forty-eight. What are the advantage and disadvantage of induction type instruments?

Overview

The document elaborates on the operational principles of deflection-type meters, discussing key aspects such as controlling torque, grounding, and damping mechanisms. It serves as an informative resource for understanding electrical measurement techniques and instruments like galvanometers and ammeters.

Key Points

1Deflection-type meters convert electrical energy to mechanical energy for measurement
2Controlling torque is vital for limiting pointer deflection and ensuring accuracy
3Grounding protects users from electric shock and equipment from damage
4Damping is essential to stabilize pointer movement for accurate readings
5Moving coil instruments are unsuitable for AC due to the rapid current direction changes

Details

Category: Technology and Engineering

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