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# Multi-Range Analog Ammeter - PowerPoint PPT Presentation

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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## PowerPoint Slideshow about ' Multi-Range Analog Ammeter' - keaton-fowler

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Presentation Transcript

• 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

ECE 201 Circuit Theory I

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

Flux “Bunching”

Mechanical forces on the conductor

ECE 201 Circuit Theory I

• 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

• Ishunt = ILoad - Imeter

• Parallel combination of meter and shunt

• ImeterRmeter = IshuntRshunt

• Rshunt = Rmeter(Imeter/Ishunt)

• Need to know Rmeter !

Imeter

Ishunt

ECE 201 Circuit Theory I

• 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 movement

• 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