Encoder interface walkthrough
The 6ES7138-4DB03-0AB0: Short-circuit and reverse polarity protection are built in, and the module supports hot-swap (module exchange under process voltage). Galvanic isolation exists between channels and the backplane bus, but not between the channels and L+. The output voltage for the encoder is L+ minus 0.8 V, so account for a small drop when cabling to remote encoders. Draw up to 40 mA from L+ unloaded and 10 mA from backplane bus. Total dissipation 1 W typical.