Different types of Ammeter & Voltmeter

Introduction

Ammeters and voltmeters are essential instruments used in electrical measurements. They play a crucial role in measuring current and voltage, respectively. Understanding the fundamentals of ammeters and voltmeters is essential for accurate measurements and ensuring the safety of electrical systems.

Types of Ammeter

PMMC (Permanent Magnet Moving Coil) Ammeter

The PMMC ammeter operates on the principle of the interaction between a permanent magnet and a moving coil. It is widely used due to its accuracy and simplicity. The construction consists of a permanent magnet, a coil suspended on jewel bearings, and a pointer attached to the coil. When current flows through the coil, it experiences a torque that moves the pointer on the calibrated scale.

Advantages of PMMC Ammeter:

• High accuracy
• Low power consumption
• Wide operating range

Disadvantages of PMMC Ammeter:

• Limited overload capacity
• Susceptible to external magnetic fields

Real-world applications of PMMC Ammeter:

• Laboratory experiments
• Electrical equipment testing

MI (Moving Iron) Ammeter

The MI ammeter operates on the principle of the interaction between a fixed coil and a moving iron piece. The construction consists of a coil wound on a soft iron core and a pointer attached to the iron piece. When current flows through the coil, it generates a magnetic field that attracts the iron piece, causing the pointer to move.

Advantages of MI Ammeter:

• High overload capacity
• Insensitive to external magnetic fields

Disadvantages of MI Ammeter:

• Lower accuracy compared to PMMC ammeter
• Higher power consumption

Real-world applications of MI Ammeter:

• Industrial power distribution
• Electrical panel monitoring

Electrodynamometer Ammeter

The electrodynamometer ammeter operates on the principle of the interaction between two coils. One coil carries the current to be measured, while the other coil carries a current proportional to the square of the measured current. The interaction between these coils produces a deflecting torque that moves the pointer.

Advantages of Electrodynamometer Ammeter:

• High accuracy
• Wide operating range

Disadvantages of Electrodynamometer Ammeter:

• High power consumption
• Sensitive to external magnetic fields

Real-world applications of Electrodynamometer Ammeter:

• Power system analysis
• Electrical equipment calibration

Induction Ammeter

The induction ammeter operates on the principle of electromagnetic induction. It consists of a current-carrying coil and a metal disc. When current flows through the coil, it generates a magnetic field that induces eddy currents in the disc. The interaction between the magnetic field and the eddy currents produces a deflecting torque that moves the pointer.

Advantages of Induction Ammeter:

• High overload capacity
• Insensitive to external magnetic fields

Disadvantages of Induction Ammeter:

• Lower accuracy compared to PMMC and MI ammeter
• Limited operating range

Real-world applications of Induction Ammeter:

• Industrial motor control
• Electrical machinery monitoring

Types of Voltmeter

PMMC (Permanent Magnet Moving Coil) Voltmeter

The PMMC voltmeter operates on the same principle as the PMMC ammeter. It measures voltage by utilizing the interaction between a permanent magnet and a moving coil. The construction and working of the PMMC voltmeter are similar to the PMMC ammeter.

Advantages of PMMC Voltmeter:

• High accuracy
• Low power consumption
• Wide operating range

Disadvantages of PMMC Voltmeter:

• Limited overload capacity
• Susceptible to external magnetic fields

Real-world applications of PMMC Voltmeter:

• Laboratory experiments
• Electrical equipment testing

MI (Moving Iron) Voltmeter

The MI voltmeter operates on the same principle as the MI ammeter. It measures voltage by utilizing the interaction between a fixed coil and a moving iron piece. The construction and working of the MI voltmeter are similar to the MI ammeter.

Advantages of MI Voltmeter:

• High overload capacity
• Insensitive to external magnetic fields

Disadvantages of MI Voltmeter:

• Lower accuracy compared to PMMC voltmeter
• Higher power consumption

Real-world applications of MI Voltmeter:

• Industrial power distribution
• Electrical panel monitoring

Electrodynamometer Voltmeter

The electrodynamometer voltmeter operates on the same principle as the electrodynamometer ammeter. It measures voltage by utilizing the interaction between two coils. The construction and working of the electrodynamometer voltmeter are similar to the electrodynamometer ammeter.

Advantages of Electrodynamometer Voltmeter:

• High accuracy
• Wide operating range

Disadvantages of Electrodynamometer Voltmeter:

• High power consumption
• Sensitive to external magnetic fields

Real-world applications of Electrodynamometer Voltmeter:

• Power system analysis
• Electrical equipment calibration

Induction Voltmeter

The induction voltmeter operates on the same principle as the induction ammeter. It measures voltage by utilizing electromagnetic induction. The construction and working of the induction voltmeter are similar to the induction ammeter.

Advantages of Induction Voltmeter:

• High overload capacity
• Insensitive to external magnetic fields

Disadvantages of Induction Voltmeter:

• Lower accuracy compared to PMMC and MI voltmeter
• Limited operating range

Real-world applications of Induction Voltmeter:

• Industrial motor control
• Electrical machinery monitoring

Extension of Range of Instruments using Shunt & Multiplier

Shunt

A shunt is a device used to extend the range of an ammeter. It is connected in parallel with the ammeter to divert a portion of the current, allowing the ammeter to measure higher currents. The shunt resistance is calculated based on the desired range extension and the ammeter's internal resistance.

Advantages of Shunt:

• Allows measurement of higher currents
• Cost-effective solution

Disadvantages of Shunt:

• Increases complexity of the circuit
• Introduces additional resistance and potential errors

Real-world applications of Shunt:

• High-current electrical systems
• Industrial machinery monitoring

Multiplier

A multiplier is a device used to extend the range of a voltmeter. It is connected in series with the voltmeter to multiply the voltage being measured. The multiplier resistance is calculated based on the desired range extension and the voltmeter's internal resistance.

Advantages of Multiplier:

• Allows measurement of higher voltages
• Cost-effective solution

Disadvantages of Multiplier:

• Increases complexity of the circuit
• Introduces additional resistance and potential errors

Real-world applications of Multiplier:

• High-voltage electrical systems
• Power transmission monitoring

Conclusion

In conclusion, ammeters and voltmeters are essential instruments in electrical measurements. Understanding the different types of ammeters and voltmeters, their principles of operation, construction, advantages, disadvantages, and real-world applications is crucial for accurate measurements and selecting the appropriate instrument for specific applications. Additionally, the use of shunts and multipliers allows for the extension of the range of these instruments, enabling measurements of higher currents and voltages.

Summary

Ammeters and voltmeters are essential instruments used in electrical measurements. There are different types of ammeters, including PMMC, MI, electrodynamometer, and induction ammeters. Each type operates on different principles and has its advantages and disadvantages. Similarly, there are different types of voltmeters, including PMMC, MI, electrodynamometer, and induction voltmeters. Understanding the principles of operation, construction, advantages, disadvantages, and real-world applications of these instruments is crucial. Additionally, the use of shunts and multipliers allows for the extension of the range of ammeters and voltmeters, enabling measurements of higher currents and voltages.

Analogy

Imagine you are a detective investigating a crime scene. To gather evidence, you need different tools. Similarly, in electrical measurements, ammeters and voltmeters are like the detective's tools. They help us measure current and voltage accurately, just like the detective collects evidence to solve the case. Just as the detective has different tools for different situations, there are different types of ammeters and voltmeters for various applications.