Capacitor Help

Graham Armitage, Fri Aug 22 2014, 01:10PM

I picked a couple of these sprague electrolytics for a power supply doubler. Have to admit, this is the first time I have seen 3 leads on an electrolytic. As the photo shows, it has a typical + and - lead on one end, and then on the other end a lead that appears to be attached to the case, but marked +.

When I apply 20v to the + and - on one end and measure the voltage between the 2 positive leads I get 18.5v. No voltage reading between the negative and far end (case) positive. Anyone have an idea of how this is connected internally? I am probably just going to use the main two leads, but was curious as to what is going on?


Cap
Re: Capacitor Help
Steve Conner, Fri Aug 22 2014, 01:27PM

The can of an electrolytic capacitor usually ends up about the same potential as the negative terminal, but it shouldn't be used as a connection. The third lead on these things is probably just for mechanical support when mounting it to a PCB.
Re: Capacitor Help
Graham Armitage, Fri Aug 22 2014, 01:44PM

Perfect - that was what I was wondering. Thanks Steve for the quick response.