Ground symbol - solution - Huaqiang Electronic Network

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"Grounding" is an important symbol in the circuit diagram. It involves several concepts that are both connected and different, such as "signal ground", "connecting the casing", "protective grounding", "equal potential", etc. You must pay attention to the differences between them when drawing and reading pictures.

1. Signal ground

"Signal ground", also called "general grounding" or "grounding", refers to the common reference potential of all circuits during signal transmission. In the circuit, the zero potential is often used as the reference potential. The symbol of "signal ground" is shown in (A).

2. Pick-up case

"Connecting the casing" means the potential at which the metal casing of the electrical equipment is located. The potential of the casing is often the common reference potential of the circuit in electronic equipment, so it is often referred to as the "chassis ground." The symbol is as shown in (B), and can be drawn in the form of a diagram (C) without causing confusion. In many electronic devices, the "signal ground" is often connected to the "chassis ground". In this case, the "signal ground" in the circuit should use the "chassis ground" symbol.

3. Equipotential

When the potentials of some local common points in the circuit are equal, and these common points are different from the "signal ground", these points are represented by the "equal potential" symbol, as shown in Figure (A). In the electronic circuit diagram, if there are multiple circuits that refer to the same potential value (such as +2V), these points can be connected by a line in the drawing, and then the potential value is specified. This method of drawing will make the connection long and tortuous, affecting the drawing and reading. If equipotential symbols are used to represent the equal relationship of potentials at different equipotential levels, long wiring can be omitted and the readability of the circuit diagram can be increased.

In electronic systems where both analog and digital circuits exist, in order to prevent mutual interference between the two circuits through the ground, the "signal ground" (AGND) of the analog circuit and the "signal ground" of the digital circuit (DGND) are often required. ) Separate inside the system and put them together at the “ground” terminal of the system. At this time, “AGND” and “DGND” in the circuit diagram are represented by “equal potential” symbols, as shown in Figure (C).