Here is a guide to hooking up multiples of the Omron D40A-1C5 speed sensor. The wiring diagram on their datasheet gets busy fast. Here is an easy breakdown:
On your first sensor:
The White wire will go to D1 on the switch controller.
The Black wire will go to the white wire on the next switch
The Brown wire will go to D3 on the switch controller
Finally, the Blue wire will go to D4 on the switch controller.
The rest of your sensors (2 to 29 more) will hook up this way:
The Black wire will go to the white wire on the next switch, except the very last sensor you hook up.
-*The last black wire will go to D2 on the switch controller*
The Brown wire will connect to the brown wire
The Blue wire will connect to the blue wire
Here is the diagram I mentioned above:
