As it is correct to connect grounding

Unreasoned grounding, as a rule, leads to perception the circuit of undesirable signals. To formulate a principle of appropriate grounding it is easy, but sometimes to follow this principle heavy. This principle can be formulated so: grounding on which the loading current to the power supply flows, should be carried out by a separate wire, instead of unite with a wire of the earth of a signal.

On fig. 1 is set an example by p to realization of this principle. The sense of such grounding is that often the loading current is many times more than a signal current. A loading current, proceeding even through wires of rather big section, can cause power failure (IR) on grounding lines. It will cause tension change on lines of basic tension of each OU attached to this line of grounding. In extreme cases this change of potential can make some millivolt and can be a source of a considerable error.
/>

of the Fig. 1. Correct circuit of grounding.

A and B (in circles) - grounding wires on which the small current flows; In and G (in circles) - grounding wires on which the big current flows; 3-an earthed conclusion.
/>

Once again about grounding

Exists two techniques which even those who makes impression knowing lightly concern, is a grounding and shielding. The main reason complication which can arise in this area, is concluded in formation of so-called chains of feedback through the earth.

Rice 1. A situation leading to serious consequences — universal currents of grounding (and); correct grounding.

Such chain is created by the currents proceeding in the conductor of grounding. This current creates falling, tension which is shown for system as a signal. This situation is shown on fig. 1, and., where the signal earth, the general conductor to the power supply from the amplifier and the conductor of grounding of the power supply are connected to various currents on a grounding surface.

of the Fig. 2. A method of connection of the earth of analog and digital circuits on the printed-circuit board.

the Surface of grounding can be a massive thick piece of copper, either the earth, or a big leaf of metal, but even in this case there is no confidence that the problem is solved. If the thin wire is "earth", almost for certain you will face a problem of chains of feedback through the earth.

In a case shown on fig. 2, the big current ("big" the current in only some milliamper can be considered) causes power failure between points In and S.Eto can be interpreted as a signal of a direct current on an entrance of the amplifier. Though we can consider that the entrance signal operates between a point of L and an input line of the amplifier, actually an entrance signal for the amplifier there will be a tension concerning the Page point

We very often speak about need of grounding, but such cases when there is too much grounding points are apparently possible also. The best situation is the unique point of grounding as it is shown on fig. 1, B. Thus formation of chains of feedback through the earth is excluded or at least considerably is at a loss.

of the Fig. 2. shows, how it can be made when developing drawing of printing conductors on the printed-circuit board. Grounding conductors from various chains agree in one point on the face socket of a payment. For stronger currents two parallel conclusions are used.
/>