You can wire the npn sensor to a relay and then use the relay to signal to the Easy.
You may also be able to use a pull up resistor with the npn sensor. When the npn sensor is OFF, the resistor holds the input high. When the npn sensor is ON, it pulls the easy input low or off. If you use this method you must invert the logic in the Easy Relay. Also, you must pick the proper wattage resistor for the current or you will burn it out.
Norm Dziedzic