bench power supply

I have a power supply that has 3 holes for wires.
A red, green, and black one.

Red is +
Black is -

What do you use the green input for?

Thanks for helping!



Ground, or zero volts.

But isnĀ“t the black input zero volts or ground?
or are they both ground?

What do you measure between Red & Black? Red & Green? Black & Green? Green may be connected to mains (earth) ground, check with Ohm meter (POWER OFF) between Green & mains plug earth prong.

Thanks for the help!

You can put a jumper between black and green if you need the supply referenced to earth ground.
Otherwise your supply is floating above earth ground.


The green terminal will be connected directly to the protective ground/earth pin (I'm not sure of the exact terminology used in your territory) of the 3 core mains lead.

If left unconnected, the output voltage between the red and black terminals will be "floating", meaning that neither are connected to the protective ground/earth.

By making a connection between the green and black terminals, you get a grounded supply, with a +ve output voltage on the red terminal.

You could also connect the green to the red, and get a grounded supply, with a -ve output on the black terminal.

I would say that in more than 90% of cases you are likely to want to connect green to black.used