Ammeter

As we all know, the measurement system is related to the word “metre”. A metre is a device that can be used to measure a certain quantity. The ampere is the unit of current, as we all know. Ammeter is an abbreviation for ampere metre, which is a device that measures ampere value. An ammeter is a metre or instrument that measures current in amperes, which is the unit of current.

Ammeter

Ampere Meter is the origin of the term Ammeter. The ammeter is a type of metre found in electrical equipment. It’s used to figure out how much current is flowing across a circuit. Its measures are exceedingly precise. 

The Ammeter can measure a small amount of electricity in mili-amperes or micro-amperes. To measure the current, the ammeter is connected in series to the measuring circuit. This is because it is capable of carrying the entire circuit’s current.

The ammeter is used to measure a little quantity of current and the result is represented in mill amperes when it is kept in series with the circuit to be tested for passing the full current in the circuit through it.

Working Principle of Ammeter

The fundamental principle of an ammeter is that it must have a very low resistance as well as an inductive reactance. The ammeter has a very low impedance because it must have a very low voltage drop across it and must be connected in series because the current in a series circuit is the same.

Also, because of the low impedance, the power loss will be modest, and if connected in parallel, it will be almost a short circuited channel, with all current flowing into the ammeter, perhaps causing the instrument to burn. As a result, it needs to be connected in series. 

Types of Ammeter

Depending on the constructing Principle, there are many types of Ammeter. They are:

• Permanent Magnet Moving Coil Ammeter.
• Moving Iron Ammeter.
• Electrodynamometer type Ammeter.
• Rectifier type Ammeter.

On the Basis of Measurement we have:

• DC Ammeter
• AC Ammeter

DC ammeters are primarily PMMC instruments that can measure both AC and DC currents, as well as Electrodynamometer type thermal instruments that can measure both DC and AC. Induction metres are not commonly used for ammeter construction because of their greater cost and measurement inaccuracy.

Description of Different Types of Ammeters

PMMC Ammeter

When a current-carrying conductor is placed in a magnetic field, a mechanical force occurs on the conductor; if the conductor is connected to a moving system, the pointer moves along the scale as the coil moves.

Explanation: Permanent magnets, as the name implies, are used in these types of measuring tools. Since the deflection of the pointer is proportional to the current, if the current direction is reversed, the deflection of the pointer will also be reversed, it is only usable for DC measurements. 

This instrument is referred to as a  D’Arsonval type instrument. It has the following advantages: linear scale, low power consumption, and excellent precision. The fact that only DC quantities are measured has a number of drawbacks, including increased costs.

Deflecting Torque

T=BiNlb     Nm

Where,
B = Flux density in Wbm2.
i = Current flowing through the coil in Amp.
l = Length of the coil in m.
b = Breadth of the coil in m.
N = No of turns in the coil.

Extension of Range in a PMMC Ammeter:

It now appears to be quite remarkable that we can enhance the measurement range in this type of sensor.

Many of us will believe that we need to purchase a new ammeter or change the constructional feature so that we can measure higher currents, but this is not the case; all we need to do is connect a shunt resistance in parallel and the instrument’s range will be extended; this is a simple solution provided by the instrument.

MI Ammeter

It is a moving iron instrument that can be used for both AC and DC. It can be used for both because the deflection is proportional to the current, therefore it shows directional deflection regardless of current direction. Its Torque equation is:

T=12I2dLdθ

Here, 

I is the total current flowing in the circuit in Amp.
L is the self-inductance of the coil in Henry.
θ is the deflection in Radian.

They are further categorized in two ways:

Attraction Type

When an unmagnetised soft iron is placed in a magnetic field, it is attracted to the coil; however, if a moving system is attached and current is passed through a coil, it creates a magnetic field that attracts the iron piece and produces deflecting torque, causing the pointer to move over the scale.

Repulsion Type

When two iron pieces are magnetized with the same polarity by passing a current, they repel each other, causing a deflecting torque that causes the pointer to move.

MI instruments have the following advantages: they can measure both AC and DC, are inexpensive, have low friction errors and are sturdy, and so on. It’s mostly used in AC measurements because hysteresis causes more mistakes in DC measurements.

Rectified Ammeter

They are used for AC measurement and are connected to the secondary of a current transformer, where the secondary current is significantly lower than the primary, and then to a moving coil ammeter through a bridge rectifier.

Advantages

• It is also useful in High Frequency.
• Uniform Scale for most of the ranges.

Application of Ammeter 

There are the following applications of ammeter listed below. This are as follows:

• This gadget comes in a variety of ranges and is commonly used in laboratories and enterprises.
• It can also be used to check the current flow in the house’s electrical devices.
• It’s also popular in companies that specialize in manufacturing or instrumentation.
• A thermocouple and an ammeter can be used to check the temperature.
• Electricians use this gadget to look for circuit issues in companies and households.

Conclusion

Ampere Meter is the origin of the term Ammeter. The ammeter is a type of metre found in electrical equipment. It’s used to figure out how much current is flowing across a circuit. Its measures are exceedingly precise. The ammeter is used to measure a little quantity of current and the result is represented in mill amperes when it is kept in series with the circuit to be tested for passing the full current in the circuit through it.

The fundamental principle of an ammeter is that it must have a very low resistance as well as an inductive reactance. The ammeter has a very low impedance because it must have a very low voltage drop across it and must be connected in series because the current in a series circuit is the same.