I just purchased an adjustable DC power supply.

https://www.amazon.com/Variable-Eventek-Adjustable-Regulated-Alligator/dp/B07DQR177D enter image description here It has three terminals : "-"(black), "ground"(green) and "+"(red).

When I test it with multi-meter, there is no voltage between the negative rail and the ground rail. Same for the voltage between the ground rail and the positive rail.

When I connect the negative rail and the positive rail together, it works correctly. However, this is not why I bought an adjustable DC supply with 3 terminals.

I bought it so that I can use operational amplifiers...

What would the purpose of this ground terminal?

Is there a way that I can use this adjustable DC power supply as I want to use it?

  • \$\begingroup\$ When you say you want to power opamps, do you mean split power supply as in +-12 V? If yes, then you need a dual power supply. \$\endgroup\$
    – winny
    Jul 13, 2018 at 7:24

1 Answer 1


The green terminal is true earth ground. It is connected to the ground lug on the ac power cord, which should ultimately be connected to a ground rod. The output of the power supply would seem to be isolated from ground, meaning that neither the positive or negative terminal is connected to ground.

For work with operational amplifiers you probably want a symmetrical bipolar power supply, which outputs both a positive and negative voltage having the same magnitude. Both of these voltages are with respect to a third common output. Such a supply would likely have four terminals where the fourth was the green earth ground.

  • \$\begingroup\$ Thank you Elliot. I was thinking about the same thing about the symmetrical bipolar power supply. I guess I would have to return this one then. \$\endgroup\$
    – user167987
    Jul 13, 2018 at 0:04
  • \$\begingroup\$ @user167987 it's a fair assumption that this power supply's outputs are isolated from mains. As a result, rather than returning it, you could buy a second one and wire them up appropriately :) up to you but. \$\endgroup\$
    – DSWG
    Jul 13, 2018 at 2:49
  • \$\begingroup\$ @DSWG Yeah. That's what I am trying to do but this one is 50€ more expensive than the one with 2 terminals... So I am returning it to get a cheaper one :) \$\endgroup\$
    – user167987
    Jul 13, 2018 at 13:33

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