Hi Ronald
use the 24V supply as the G540's 48V supply is more than the sensors 6 - 36V supply range
as the sensor has a N/C NPN output you can only connect one sensor directly to each G540 input
the G540 input circuit consists of the LED within an opto isolator that is connected in series with a 2200 ohm resistor powered from a +12V supply
when an input is grounded approximately 4.5 mA will flow from the G540 input to ground
you can measure this with a multimeter connected between the input and G540 ground
(the current is limited by the 2200 ohm resistor inside of the G540)
John