AC and DC meters

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AC and DC meters
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Ammeter
Ammeter is an electrical measuring device, which
is used to measure electric current through the
circuit. CONNECTION OF AMMETER IN CIRCUIT An
ammeter is always connected in series to a
circuit. SYMBOL
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Ammeter

• Ammeter is a low resistance galvanometer
• It is used to measure the current in a circuit in
  amperes
• Galvanometer can be converted into an ammeter by
  using a low resistance wire in parallel with the
  galvanometer
• the resistance of the wire depends upon the
  range of the ammeter
• As shunt resistance is small the combined
  resistance of the galvanometer the shunt is
  very low hence the ammeter has much lower
  resistance than galvanometer
• An ideal ammeter has zero resistance

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Voltmeter
Voltmeter is an electrical measuring device,
which is used to measure potential difference
between two points in a circuit. CONNECTION OF
VOLTMETER IN CIRCUIT Voltmeter is always
connected in parallel to a circuit. SYMBOL  
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Voltmeter

• Volt meter is a high resistance galvanometer
• It is used to measure the potential difference
  between two points of a circuit in volts
• A galvanometer can be converted into a volt meter
  by using a high resistance in series with the
  galvanometer
• The value of resistance depends upon the range of
  the volt meter
• For voltmeter a high resistance, R is connected
  in series with the galvanometer therefore
  resistance of voltmeter is very large as compared
  to that of galvanometer
• The resistance of an ideal voltmeter is infinity

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Ohmmeter

• The purpose of an ohmmeter, is to measure the
  resistance placed between its leads.
• This resistance reading is indicated through a
  mechanical meter movement which operates on
  electric current.
• The ohmmeter must then have an internal source of
  voltage to create the necessary current to
  operate the movement
• Also have appropriate ranging resistors to allow
  just the right amount of current through the
  movement at any given resistance

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Simple ohmmeter circuit
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Multimeter

• A multimeter is a device used to measure
  electrical current, voltage, and resistance.A
  multimeter combines several electrical meters
  into one handheld unit.
• Basic multimeter models can measure voltage,
  current and resistance.
• Advanced models can also measure temperature,
  inductance, capacitance, duty cycle and
  frequency.
• They can also test diodes and transistors.
• Some even work as an oscilloscope.
• The two main types of multimeter are digital and
  analogue

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