Connect GND/signal-output-pins to differential-input-pins
When both devices are not connected in any other way except for their output and input  terminals, you can just connect as described: connect GND to one of the diff. input-pins and signal to the other diff. input-pin.

connections in any other way include shared earth or chasis or signal ground.

EDIT after new presented information
Devices that allow for differential inputs sometimes also specify an allowable common mode voltage. Check the datasheet of the input device for this allowed common mode voltage.