ABB 1SNA684252R0200工控DCS系统PLC模块

ABB 1SNA684252R0200工控DCS系统PLC模块

ABB 1SNA684252R0200工控DCS系统PLC模块

1.1.2逻辑地：也叫机器逻辑地、主机电源地，是计算机内部的逻辑电平负端公共地，也是+5V等的电源输出地。如CPU的正负5伏、正负12伏的负端。需要接入公共接地极。 　　

1.1.3屏蔽地（AG，Analog Grounding） 也叫模拟地，它可以把现场信号传输时所受到的干扰屏蔽掉，以提高信号精度。DCS系统中信号电缆的屏蔽层应做屏蔽接地。线缆屏蔽层必须一端接地，防止形成闭合回路干扰。铠装电缆的金属铠不应作为屏蔽保护接地，必须是铜丝网或镀铝屏蔽层接地。接入公共接地极。 　　

1.1.4本安地 应独立设置接地系统，接地电阻≤4Ω。本安地的接地系统应保持独立，与厂区电气地网或其它仪表系统接地网的距离应在5m以上。

ABB 1SNA684252R0200工控DCS系统PLC模块

1.1.2 Logic: also called machine logic, host power supply, is the internal logic level of the negative end of the public, but also +5V power output. For example, the negative end of the CPU is plus or minus 5 volts and plus or minus 12 volts. The common ground pole needs to be connected.

1.1.3 Shielded ground (AG, Analog Grounding), also called analog ground, can shield the interference caused by the on-site signal transmission to improve the signal accuracy. The shield layer of signal cable in DCS system should be grounded. One end of the cable shielding layer must be grounded to prevent closed loop interference. The metal armor of armored cables should not be used as shielding protection grounding, and must be grounded by copper wire mesh or aluminum-plated shielding layer. Connect to the common ground pole.

1.1.4 The grounding system should be set up independently with a grounding resistance ≤4 ohms. The grounding system of the local safe ground should be independent, and the distance from the electrical grounding network or other instrument system grounding network of the plant should be more than 5m.