I-7088 and M-7088 User Manual, Rev: A1.2 7MH-026-A12
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A.3. Frame Ground
Electronic circuits are constantly vulnerable to Electro-Static
Discharge (ESD), which become worse in a continental climate area.
Some I-7000 and M-7000 modules feature a new design for the
frame ground, which provides a path for bypassing ESD, allowing
enhanced static protection (ESD) capabilities and ensures that the
module is more reliable.
Either of the following options will provide a better protection for the
module:
1. If the module is DIN-rail mounted, connect the DIN-rail to the earth
ground. This is because the DIN-rail is in contact with the upper
frame ground, as shown in the figure below.
2. Alternatively, connect the lower frame ground terminal to a wire
and connect the wire to the earth ground, as shown in the figure
below.