Measuring Capacitance using a basic Multimeter

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Discussion Overview

The discussion revolves around methods to measure the capacitance of a capacitor using a multimeter that lacks a direct capacitance measurement feature. Participants explore various indirect techniques, circuit configurations, and considerations regarding accuracy and component values.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • Some participants propose constructing a circuit with a battery, resistor, and capacitor to measure the time for the voltage drop across the capacitor, using the RC circuit equation.
  • Others discuss the importance of the multimeter's input resistance and how it may affect measurements, particularly for smaller capacitance values.
  • One participant suggests using a switch to facilitate measuring charge and discharge times, emphasizing the need for proper circuit configuration.
  • Some participants mention alternative methods, such as using known capacitors to determine the voltage after connecting to an unknown capacitor or employing a constant current supply for linear voltage increase over time.
  • Concerns are raised about the reliability of multimeters in measuring capacitance, with some sharing personal experiences of inconsistent readings.
  • Participants discuss the potential for using a resistance measurement to charge the capacitor and then measuring the voltage decay rate as a simplification of external circuitry.

Areas of Agreement / Disagreement

There is no consensus on a single method for measuring capacitance, with multiple competing views and techniques being proposed. Participants express varying degrees of confidence in the methods discussed, and some raise concerns about the accuracy and reliability of measurements.

Contextual Notes

Participants highlight limitations related to the accuracy of measurements, the dependence on multimeter specifications, and the need for careful circuit design to avoid errors in readings.

  • #31
ARoyC said:
Thank you so much for the solution!
So are you going to put it together and see what values of C (using what values of R?) you can measure pretty accurately? That's the fun part of the project... :smile:
 
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  • #32
ARoyC said:
Could you please explain a bit, if possible?
You will need to experiment with a multimeter and some capacitors.

The ohmmeter works by producing a voltage difference and measuring the current, or by producing a current and measuring the voltage dropped across the resistor. When you measure the resistance of a capacitor, you charge that capacitor. When you measure the voltage of a capacitor, a small current flows through the meter, so the capacitor voltage falls towards zero.
 
  • #33
Oh, okay. That is a great idea. Thank you.
 
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