# The Ground in ATX Power Supply

Last Update Time: 2019-04-12 13:11:17

Ground is a very important concept in any circuit. Because in any circuit, voltage is one of its most essential attributes.

The specific content of the definition of voltage is not what we care about, but the relativity of voltage: that is, voltage is a physical property describing the work of electric field force between two points (in fact, the physical quantity of energy square). Although we often use such sentences as "what is the voltage at a certain point", it does not mean that "a certain point" really has the property of voltage. This is only an ellipsis. The complete statement is as follows: What is the voltage of a point (relative to the reference point)?

Let's look again at the instruments that can be used to measure voltage, such as the multimeter (oscilloscope). The multimeter has red and black pens. When measuring the voltage at a certain point in the circuit, we will use the tip of one of the red and black pens to touch the point. What about the other pen?

If the other pen doesn't pick up anywhere, the multimeter will show 0V. At this time, 0V does not mean that the voltage at this point is 0V. It is actually the initial state of the multimeter reading. Only when another pen is connected to other points in the circuit, the reading displayed by the multimeter is the voltage value between "one point" and "other points".

It can be seen that this "other point" is actually optional. In this case, why not choose the most convenient and meaningful point as the reference point? The answer is yes, that is " GND".

"GND" is the abbreviation of the ground. It is the real land that people tread on under their feet.

Is it true that all the points / lines marked "ground" are connected to the earth? As far as security norms are concerned, this should indeed be the case. That's why many devices have three pieces of metal in their plugs. One of them is used to connect to the earth, and the other end of the earth wire in the socket should indeed be reliably connected to the earth through a conductor.