Instrumentation: ground and noise

1
Instrumentation ground and noise
Temperature Measurement
2
Grounding
3
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.

4
Conductive Coupling
Large current flowing through the load causes Va?
Vb.
Solution
5
Capacitive Coupling Electric Field
Solution Shielding
6
Inductive Coupling Magnetic Field
Hard to eliminate shielding and twisted-pair
wire