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7.2.2 Equipment grounding design
E21Internal circuit grounding
E21 is floating ground equipment. The signal ground is isolated from ground by high
resistance return circuit (LC filter network, optical coupler, RC network).
To avoid static electricity accumulation by system or high frequency interference,
signal ground is usually connect to the ground by RC net.
RC network of E21 is integrated inside the product with one end connect to signal
ground, and the other end connect to ground (three pins of POWER terminal), as
shown in Figure 7-1.
Figure 7-1 Internal Grounding Diagram
E21Chasis grounding
E21 enclosure is conductive metal, and must be low resistance grounding, which can
effectively reduce short circuit or danger caused by system fault. Low resistance
grounding can also significantly reduce external interference to system or system
interference to the outside.
Principal measures of E21 enclosure grounding are: there is a grounding terminal
outside of enclosure. The terminal must be grounded, with grounding resistance no
higher than 0.3 ohm.
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