Parasitic capacitance influence on lead voltage

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Discussion Overview

The discussion revolves around the influence of parasitic capacitance on voltage readings in an RC circuit, particularly in scenarios where the voltage (V') changes rapidly and chaotically. Participants explore the implications of this capacitance on reading accuracy at a frequency of 50 Hz.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant inquires about determining the influence of parasitic capacitance (~50 pF) on V' and its effect on reading accuracy, particularly when τ=RC>0.02 sec.
  • Another participant suggests that the nature of V' changes (e.g., whether it is a sine wave or arbitrary) significantly affects the complexity of the analysis.
  • A third participant notes that V' changes chaotically, complicating the analysis further.
  • It is mentioned that existing tools for analyzing circuits typically assume a steady state or periodic steady state, which may not apply in this case.
  • One participant indicates that the only way to deduce the output from an arbitrary input in this RC circuit is by solving the differential equation of the system.

Areas of Agreement / Disagreement

Participants express differing views on the nature of V' changes and the implications for analysis. There is no consensus on a specific method for addressing the influence of parasitic capacitance given the chaotic nature of V'.

Contextual Notes

The discussion highlights limitations in applying standard analysis tools to non-periodic or chaotic signals, as well as the dependence on the specific characteristics of V' changes.

Marcis Rancans
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V' changes over time. How can I determine the influence from parasitic capacitance (~50 pF) on V?
R wire ~ 100 ohm. If I need to read data (V' can change rapidly) from this at 50hz, does it influence reading accuracy? How can I determine values from which I need to be careful when reading data (when τ=RC>0,02sec ?)

https://lh5.googleusercontent.com/YxtTJvFj8vYphq43bW3FTw0ygk7D0WOJPVmzetsrsRsbclgyXy9ErGz6jA=s300
 
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This will all depend on how V' is changing over time. Is it a sine wave? Then the solution will be relatively straightforward to calculate. If V' changes arbitrarily, it won't be nearly as easy :)
 
rumborak said:
This will all depend on how V' is changing over time. Is it a sine wave? Then the solution will be relatively straightforward to calculate. If V' changes arbitrarily, it won't be nearly as easy :)
V' changes chaotically.
 
The problem is, all the easy tools that exist for analyzing circuitry presume a steady state, or at least a "periodic steady state".
What you have there is a type of RC circuit, and the only way to deduce the output from an arbitrary input is by solving the differential equation of that system.
For more:

http://en.m.wikipedia.org/wiki/RC_circuit
 
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