Hardware 3.3.2 Earthing The metal housing is to be connected to earth. Each side wall has an earthing connector integrated into it (see arrow in illustration): Fig. 6: Earthing connector Ш Type of connector Connect plain plug 6.3 x 0.8 mm (fast-on) to at least 1 of the side walls Ш Earthing lead Diameter: min. 2.5 mmІ Length: as short as possible Ш Function: earth connection of functions. No protection against high contact voltage. To ensure the protective function, make sure that the devices are supplied with safely separated small voltages (see chapter 2.4.1). Ш The casing of the COM1 connector for the serial port directly connects to the earth connection of functions.
This is where you attach the cable shielding. Ш The connectors for +24V DC and 0V supply are inter- nally (by spring contacts on the PCB) and capacitively connected to the housing and, thus, to earth. High- frequency interference is conducted to earth via this channel. 26