Exam II

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Exam II
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Exam 2

• 1. (20 pts) Short questions
• (4 pts) What does power factor equal one imply?
• Power supplied by the source is dissipated on the
  resistor.
• Or the load is resistive.
• Or The imaginary part of complex power is zero.
• (4 pts) How do you distinguish 120 V and 240 V
  outlets at your home?
• 120V three prongs
• 240V Four prongs
• (4 pts) How does the ground fault circuit
  interrupter (GFCI) work?
• Detect the current difference between the hot and
  ground wires. If the value is larger than a set
  value, it will disconnect the hot wire.
• (4 pts) List two advantages of using digital
  circuit?
• Functions are easy to achieve with circuits
• High accuracy
• (e) (4 pts) State the phase relation between
  current and voltage for capacitive load and
  inductive load, respectively.
• Capacitive load current leads voltage
• Inductive load Voltage leads current.

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Exam 2 2
Green Supercell C Red supercell A Blue
supercell B f((A,B,C)ABC
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Exam 2 3
Q0 0 1 Q2Q1 00 1 0 01 1 0 11 x x 10 0
x
D0Q2Q0( Q2Q0) Q2 NOR Q0
Q0 0 1 Q2Q1 00 0 1 01 1 0 11 x x 10 0
x
D1Q0Q1 Q1Q0 Q2 XOR Q0
D2Q0Q1 Q0 AND Q1
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Instrumentation ground and noise
Temperature Measurement
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Grounding
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Noise Sources and Coupling

• Noise sources are always present and are often
  impossible to eliminate completely.
• Sources fluorescent light fixtures, video
  monitors, power suppliers, switching circuits,
  high voltage (current) circuits.
• Affect measuring circuit by conductive
  coupling, capacitive coupling, inductive
  coupling, and radiative coupling.

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Conductive Coupling
Large current flowing through the load causes Va?
Vb.
Solution
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Capacitive Coupling Electric Field
Solution Shielding
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Inductive Coupling Magnetic Field
Hard to eliminate shielding and twisted-pair
wire