# Finding the circuit ground

A Ground part or a Zero volt rail included in your circuit acts as a reference point for measuring voltages. Otherwise any power supply which is defined relative to an external ground can set the reference point. For example:

- A positive voltage rail
- A negative voltage rail
- A variable voltage supply.

If power supplies or parts with a hidden supply are not present, a part terminal is the circuit ground. It is the bottom terminal of the first part in the following list:

- Battery
- Signal generator.

Add an explicit circuit ground to make sure which point in the circuit is grounded. If you have power supplies or parts with a hidden supply, you should always add a circuit ground.

## See also:

- Ground
- Using electronics parts