Using Dip Meter to Measure Capacitance

One of the many useful measurements a grid dip meter or grid dip oscillator can perform is to measure the capacitance of a capacitor.

Dip Meter Tutorial Includes:
Dip meter / GDO basics     How to use a dip meter / GDO     Using GDO to measure inductance     Using GDO to measure capacitance     Measuring antenna resonant frequency     Measuring feeder electrical length    

Although capacitor values are normally marked onto capacitors, there are sometimes occasions when this may not be visible, or when the value is being questioned.

On these occasions it is possible to use a grid dip meter to measure the value of the capacitor in conjunction with a known inductor.

Although inductors are not always easy to come by, there may be occasions when using a grid dip meter to measure capacitance can be of great can help.

How to measure capacitance with a grid dip meter / oscillator

The method used to measure the capacitance of an unknown capacitor with a grid dip meter is relatively straightforward. The method used, is essentially the same as that used to determine the value of an unknown inductor. It involves connecting a known inductor in parallel with the unknown capacitor to make parallel resonant circuit.

With the known inductor connected, the grid dip meter or grid dip oscillator can be used in the normal way to determine the resonant frequency of the resonant circuit.

Once the resonant frequency has been found it is a relatively straightforward calculation to determine the value of the capacitor. It can be found from the formula:

C = 1 4 Π 2 f 2 L

Where
    π = 3.142
    f = frequency of resonance (i.e. point of the maximum dip)
    C = value of capacitor in Farads
    L = value of the inductor in Henries

Ian Poole   Written by Ian Poole .
  Experienced electronics engineer and author.



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