Ammeter

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Topic
Ammeter
Presenter Hammad Ashfaq
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Definition

• An ammeter is an instrument that measures
  electric current, usually in units of amperes (or
  milliamps or micro amps when very small currents
  are involved). Both the magnitude of direct
  current (DC) and alternating current (AC) can be
  measured, though with ammeters of different types.

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The earliest design of an ammeter

• The earliest design of an ammeter was invented by
  a french guy called D'Arsonval in 1882.
• It was called galvanometer and was a mechanical
  device

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Diagram
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Basic types of Ammeter

• There are two basic types of ammeters.
• 1. The moving coil ammeter
• 2. The moving iron or moving magnet ammeter

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Principles of Ammeter

• Both versions use a principle discovered by Hans
  Christian Oersted in 1820, which holds that an
  electric current in a wire produces a magnetic
  field.
• The magnetic field exerts a force on a coil,
  making it turn.
• A pointer that is attached to the coil or magnet
  also moves, allowing the measurement to be read
  off the scale.

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Principles of Ammeter

• The moving coil ammeter has three basic parts a
  permanent magnet, a coil, and a coil spring.

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Principles of Ammeter

• When current is passed through the coil it
  creates a magnetic field that is opposite that of
  the permanent magnet, causing the coil, and its
  attached pointer, to pivot.
• The coil spring not only limits the distance the
  coil can rotate, but the amount of tension it
  exerts depends on the strength of the force
  turning the coil.

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Working of An Ammeter

• An ammeter is placed in series with a circuit
  element to measure the electric current flow
  through it.
• The meter must be designed offer very little
  resistance to the current so that it does not
  appreciably change the circuit it is measuring.

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Working of An Ammeter

• A small resistor is placed in parallel with the
  galvanometer to shunt most of the current around
  the galvanometer.
• Its value is chosen so that when the design
  current flows through the meter it will deflect
  to its full-scale reading.

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Working of An Ammeter

• Digital ammeter designs use an analog to digital
  converter (ADC) to measure the voltage across the
  shunt resistor.
• The digital display is calibrated to read the
  current through the shunt.

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Modern Working System

• Digital displays are extremely accurate and
  easy to operate, but they are more expensive than
  their electro-mechanical cousins.

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Uses

• Sometimes referred to as an ammeter, the ammeter
  can be utilized in a number of different fields.
• The device is handy for measuring the flow of
  current through the wiring systems of new
  buildings, ensuring the wiring is up to
  acceptable local safety codes.

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Uses

• Electricians will often make use of an ammeter to
  spot problems with wiring systems in older
  buildings.
• Circuit breaker with integrated ammeter
• In general, the ammeter can be utilized in just
  about any situation where it is possible to tap
  into a circuit and execute a measurement.

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Uses

• Companies that manufacture electrical equipment
  of just about any kind will make use of an
  ammeter in testing the products before offering
  them for sale.

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Advantages

• We can measure the current more accurate in the
  circuit.
• No ganger of shock by measuring current.

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