Question about electrolytic capacitors

[freddiekarten]

e cap negaive to ground

Hi all,

Just a simple question on the use of e-caps.

We all know that e-caps block DC when fully charged and allow AC to pass (most) of the time. What I'd like to know is,

1) if I tap the output of the e-cap from the negative terminal, with reference to ground (with my digital multimeter set to Vdc), would I get a negative voltage readout?

2) I've always known to connect the positive terminal to positive terminal (or terminal with the higher potential), so why do some circuits reverse this connection? Does the e-cap perform some form of inversion of voltage?

Regards,
FK

 

[papyaki]

Re: Electrolytic Capacitors

Hi,

Postive terminal must always be connected to the higher DC voltage relative to reference voltage. Negative terminal of the same capacitor must always be connected to lower DC voltage relative to reference voltage. In this case, measuring DC voltage difference between positive terminal and negative terminal will always give a positive value.

Example : Assume reference voltage is equal to 0V and two DC voltages sources are available. First one is equal to +12V (relative to 0V) and second one is equal to -12V (relative to 0V). You need to connect 2 e caps, one on each DC source and 0V.

First e cap positive terminal must be connected to +12V, negative terminal of this capacitor must be connected to 0V. Voltage difference between positive and negative terminal is positive (+12 - 0) = +12.

Second e cap positive terminal must be connected to 0V. Negative terminal must be connected to -12V. Voltage difference between positive and negative terminal is positive (0 - (-12)) = +12.

E cap dont have inverter properties.