LG, in another thread you stated:
What I wanted you to realise was that for an electrolytic capacitor to work correctly it needs a DC polarising voltage to make the dielectric form the thin insulating layer between the plates.
Measuring an electrolytic capacitor which has been previously used but now discharged, you will get a reasonable measure of its capacitance.
Also, the thickness of the dielectric layer can vary with the amount of polarising voltage (ie the DC voltage across the capacitor), and as the dielectric varies, so will the capacitance.
So, going around in circles, if you need to know accuratly the capacitance of an electrolytic capacitor, you must also consider the DC polarising voltage.
If you look at the specifications of electrolytic capacitors, the tolerance is very wide, usually -50% to +100%. So wide you could drive a Barnsley bus through it!
JimB
And I responded:I cant see a valid reason you would want to charge the cap up????????
How would you test an electrolytic capacitor?
Does the capacitance vary with polarising voltage?
What I wanted you to realise was that for an electrolytic capacitor to work correctly it needs a DC polarising voltage to make the dielectric form the thin insulating layer between the plates.
Measuring an electrolytic capacitor which has been previously used but now discharged, you will get a reasonable measure of its capacitance.
Also, the thickness of the dielectric layer can vary with the amount of polarising voltage (ie the DC voltage across the capacitor), and as the dielectric varies, so will the capacitance.
So, going around in circles, if you need to know accuratly the capacitance of an electrolytic capacitor, you must also consider the DC polarising voltage.
If you look at the specifications of electrolytic capacitors, the tolerance is very wide, usually -50% to +100%. So wide you could drive a Barnsley bus through it!
JimB