The best way to ground your application is to ensure that all the common and ground connections of your S7-200 and related equipment are grounded to a single point. This single point should be connected directly to the earth ground for your system. For improved electrical noise protection, it is recommended that all DC common returns be connected to the same single-point earth ground. Connect the 24 VDC sensor supply common (M) to earth ground. All ground wires should be as short as possible and should use a large wire size, such as 2 mm2 (14 AWG). When locating grounds,. | Installing the S7-200 Chapter 3 Guidelines for Grounding the S7-200 The best way to ground your application is to ensure that all the common and ground connections of your S7-200 and related equipment are grounded to a single point. This single point should be connected directly to the earth ground for your system. For improved electrical noise protection it is recommended that all DC common returns be connected to the same single-point earth ground. Connect the 24 VDC sensor supply common M to earth ground. All ground wires should be as short as possible and should use a large wire size such as 2 mm2 14 AWG . When locating grounds remember to consider safety grounding requirements and the proper operation of protective interrupting devices. 3 Guidelines for Wiring the S7-200 When designing the wiring for your S7-200 provide a single disconnect switch that simultaneously removes power from the S7-200 CPU power supply from all input circuits and from all output circuits. Provide overcurrent protection such as a fuse or circuit breaker to limit fault currents on supply wiring. You might want to provide additional protection by placing a fuse or other current limit in each output circuit. Install appropriate surge suppression devices for any wiring that could be subject to lightning surges. Avoid placing low-voltage signal wires and communications cables in the same wire tray with AC wires and high-energy rapidly switched DC wires. Always route wires in pairs with the neutral or common wire paired with the hot or signal-carrying wire. Use the shortest wire possible and ensure that the wire is sized properly to carry the required current. The connector accepts wire sizes from 2 mm2 to mm2 14 AWG to 22 AWG . Use shielded wires for optimum protection against electrical noise. Typically grounding the shield at the S7-200 gives the best results. When wiring input circuits that are powered by an external power supply include an overcurrent protection device in that .
