How to connect 5V sensor to Arduino nano

Hi..

I am new to Arduino, and therefore a bit confused how to wire up this sensor to an arduino nano. The sensor have 3 wires; 5V, GND and signal. The powering of the sensor I understand, but the signal wire I am a bit unsure. In the first I connected the signal wire direct to an DI pin, but then I realized arduino was very unstable with floating pin when the sensor gave 0V. Do I need to enable the pullup resistor for the DI pin? How is this working when the sensor gives 5V?

http://www.ebay.com/itm/310673782156?_trksid=p2060778.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

Hope somebody can give me a hint, thanks :)

0v is NOT floating. It should be fine without any pullup/pulldown but the only way you can be sure is if you can find a datasheet for it.

Ok, thanks. I will try one more time.