Chassis ground

As mass ( engl. chassis ground, abbreviated GND ) refers to a conductive body with the potential of 0 volts is defined in the rule, and represents the reference potential for all signal and operating voltages. (-) Most of the electrical negative pole of the supply voltage at the same time mass. The positive pole of the supply voltage ( ) and all other electrical voltages and electrical signals of an electrical circuit refers to the ground potential. Mass is the common connection of most components.

Examples in which the positive pole of the supply voltage acts as a ground potential, are mentioned below. Also in AC circuits can be defined a ground potential or connection.

Mass can be any node of an electrical circuit in principle and are used as a reference potential for the definition of all the tension in this network. The ground potential is often, but not necessarily close or equal to the ground potential. The mass is often galvanic (electric directly ) connected to the earth, which is called grounding.

In older publications, the mass is also known as a signal ground.

Ground terminal as a protective measure

Electrically conductive housing parts and accessible parts of electrical equipment with hazardous voltages are either protective conductors together and connected to earth ( the protective conductor network of electrical installation or an earth electrode ) or they are by a protective insulation safely electrically isolated from the mains (see safety class, see also ground wire).

Even when lightning relevant metal parts are included in the protective measures, ie connected and grounded.

Often, however, it is not practical, possible or allowed to connect directly to the earth ground potentials. Reasons may be large compensation or interference. In these cases must be taken to ensure that the ground potential can not accept large voltages with respect to ground, especially when (for example for reasons of electromagnetic shielding) touchable housing parts ground potential must possess.

Examples

In the automotive sector and also in motorcycles and bicycles, the ground potential is the body or frame. As the conductive part, which extends over the entire vehicle, it also serves as a return conductor for the electrical system - for every consumer must be laid only one line. In the automotive sector, the mass is across manufacturers with " Terminal 31 " refers to ( see terminal name).

It does not matter whether it is in the on-board voltage to a positive (eg automobiles in Germany ) or negative (eg, English cars ) DC or AC voltage ( eg bicycle ) is.

Telecommunication facilities such as the telephone network have historical reasons often the positive pole of their power supplies as a reference potential, this pole is also grounded. The supply voltage of telecommunications equipment, for example, -48 V and -60 V, measured with respect to ground.

Older electronics modules with germanium transistors often had the positive pole of the supply voltage as ground. Was due to the primary use of PNP transistors, the emitter terminal performs the most positive potential. Today, we used silicon transistors, which are easier to manufacture than NPN type - so that the negative was to ground.

On circuit boards, the ground potential of the largest trace, as it most of the components are connected. He is often spread as a surface over the entire printed circuit board ( ground plane, ground plane ) to avoid potential differences and interference.

For audio and analog circuits, however, signal ground and all other ground potentials in only one point ( star point ) are connected to each other to avoid interference voltages - only this point is the actual reference potential, any other places of mass can be due to voltage drops caused by high currents along the assume conductor runs slightly different potentials.

In personal computers, the ground potential is also housing and ground potential.

In high frequency systems, and assemblies, the ground potential is always connected to the housing. Also in audio amplifiers is helpful to prevent noise. In both cases it can lead to problems if this signal is connected to ground at several points with the ground ( see ground loop ground loop also ). Reasons of such compounds are the lightning protection and the protection measure protective earthing.

Help is at hand in antenna systems sheath current filter for audio equipment and laboratory isolation transformers and isolation transformers or differential inputs that allow it to interrupt the signal ground connection between devices.

Icons and Display

In the circuitry ( wiring diagram) the points to ground potential are drawn for clarity not usually associated, but each provided with a ground symbol in the real assembly symbolizes how a signal name to connect later.

In Germany, the shape of this mass icons is set according to the DIN standard. For Europe, the ISO standardization sets, has to look like the ground symbol.

Outside of devices are often mounted screw terminals for additional ground connections. This can add additional ground connections for safety (protective conductor connection ) or separate connections of the signal mass or the housing may be ( functional earth ). Both differ in the to affixed symbols ( see above) and in the conductor cross-sections and requirements attached to it.