Multi range analog ammeter
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Multi-Range Analog Ammeter. Multi-Range Multiple Full-Scale Values Ranges less than and/or greater than the device’s full-scale value Measure 10 mA with a 0-1 mA device Analog Meter Moving-pointer Works by interaction of magnetic fields. Basic Analog Meter Movement.

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Multi-Range Analog Ammeter

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Multi range analog ammeter

Multi-Range Analog Ammeter

  • Multi-Range

    • Multiple Full-Scale Values

    • Ranges less than and/or greater than the device’s full-scale value

    • Measure 10 mA with a 0-1 mA device

  • Analog Meter

    • Moving-pointer

    • Works by interaction of magnetic fields

ECE 201 Circuit Theory I


Basic analog meter movement

Basic Analog Meter Movement

ECE 201 Circuit Theory I


Interaction of magnetic fields basic dc motor

Interaction of Magnetic FieldsBasic DC Motor

Permanent Magnet Magnetic flux from N to S

Current into A and out of BMagnetic flux due to current

ECE 201 Circuit Theory I


Resulting ccw rotation

Resulting CCW Rotation

Flux “Bunching”

Mechanical forces on the conductor

ECE 201 Circuit Theory I


Extending the range of an ammeter

Extending the Range of an Ammeter

  • Meter movements available in standard full-scale values

  • We have 0 – 1 mA

  • To measure currents greater than 1 mA, we need to “divert” the extra current away from the meter using a “shunt”

ECE 201 Circuit Theory I


Calculation of the shunt resistor

Calculation of the Shunt Resistor

  • Measure ILoad

  • Ishunt = ILoad - Imeter

  • Parallel combination of meter and shunt

  • ImeterRmeter = IshuntRshunt

  • Rshunt = Rmeter(Imeter/Ishunt)

  • Need to know Rmeter !

ILoad

Imeter

Ishunt

ECE 201 Circuit Theory I


Here s how not to measure the resistance of the meter movement

Here’s how NOT to measure the resistance of the meter movement

  • Do not connect the meter movement to any analog or digital multimeter configured as an ohmmeter!

  • The internal battery will supply too much current and destroy the movement!

ECE 201 Circuit Theory I


Preliminary prelab work

Preliminary (Prelab) Work

  • Devise a non-destructive scheme to determine the internal resistance of the meter movement.

  • You may use any equipment or components (power supply, function generator, resistors, potentiometers,etc.).

  • Have your method approved BEFORE you begin the experiment!

ECE 201 Circuit Theory I


Calibration of your meter

Calibration of your Meter

  • Measure the same current with the meter you designed and a “standard” (commercial) meter.

  • Plot the reading of your meter as a function of the readings obtained with the standard meter.

ECE 201 Circuit Theory I


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