Need a lil help understanding the mesa card.. specifically the "D" card my confusion is in the 24 volt portion ... one provides 24 volts for all the ancillary options and one provides the ground ?
If you are asking about the 7I76/7I76 D difference, the only difference is that the 7I76 has sourcing field I/O outputs and the 7I76D has sinking outputs
That is the 16 7I76 field outputs source +12 or +24V to the load (so the load common is power supply common):
7I76 output --> relay coil --> common (or ground)
The 16 7I76D field outputs are sinking so load common is +12 or +24V:
thanks, yes that is what im confused about.. so the 7i76 outputs 12 or 24 volts to the relay and thats what triggers the relay to make the connection from the 12 or 24 volt main powersupply to the peripheral ?
Yes, if you think of the 7I76/7I76D outputs as switches, the 7I76 has a common +12/+24V for all 16 "switches" and the 7I76D has a common negative (ground) for all switches