Simple Resistive Circuits

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Simple Resistive Circuits

• Chapter 3.5 3.7

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Digital vs. Analog

• What is the difference between the two?

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Measuring Voltage and Current
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Measuring Voltage and Current

• Ammeter an instrument used to measure current
  which is placed in series with the circuit
  element whose current is being measured. An
  ideal ammeter has zero equivalent resistance.
• Voltmeter and instrument used to measure
  voltage which is placed in parallel with the
  circuit element whose voltage is being measured.
  An ideal voltmeter has infinite equivalent
  resistance.

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Measuring Voltage and Current

• Fluke 175 Digital Meter

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Measuring Voltage and Current

• dArsonval Movement Analog meter

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Measuring Voltage and Current
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Using a dArsonval Movement

• A 50 mV and 1 mA dArsonval movement is being
  used in an ammeter with a full scale reading of
  100 mA. Determine RA.

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Design Challenge

• You have an ammeter rated for 0 100 mA (50 mV
  and 1 mA dArsonval movement), but you need to
  measure a current from approximately 165 195
  mA. Can you design a circuit that will allow you
  to use your existing ammeter? When looking for
  parts in your toolbox you only can find a packet
  of 2 O resistors.

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Using a dArsonval Movement

• If we assume that our 0-3V or 0-15 V analog
  voltmeter uses a 50 mV and 1 mA dArsonval
  movement determine the resistors Rv for each
  configuration.

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Lecture Example Design a dArsonval voltmeter
that will have three voltages ranges as shown.
Specify R1, R2, and R3.
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Measuring Resistance with a Wheatstone Bridge
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Measuring Resistance with a Wheatstone Bridge

• What are the limitations of a Wheatstone bridge?

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Delta-to-Wye or Pi-to-Tee
Determine the equivalent resistance of the
following circuit.
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Delta-to-Wye or Pi-to-Tee
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Delta-to-Wye or Pi-to-Tee
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Delta-to-Wye or Pi-to-Tee
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Delta-to-Wye or Pi-to-Tee
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Lecture Example Use Delta-Wye transformations
to solve for v1 and v2.