Down to Ground

Dear All,

Kindly explain me the difference bet earth ground,signal ground and chasis ground

Earth ground: It's just what it sounds like. The electrical potential of the Earth. Pound a metal stake in the ground and it will be your terminal for Earth ground.

Chassis ground: The electrical potential of the frame or box that contains a device. Obviously it will be made of a conductive material. For a computer, it would be the case.

Signal ground: This one's a little trickier. It's an arbitrarily chosen (by the circuit designer) point in any given circuit assumed to have zero electrical potential (0 volts). It's useful for making measurements in a circuit.

The black lead of a power supply is typically the ground lead. In a schematic it's designated by the symbol that looks like an inverted "christmas tree".

Why is it that sensitive circuitry can be damaged if it is connected to chassis ground as opposed to signal ground. ??