hello everybody,
i am a mechsanical enginneer student and for my thesis i have to take data from a laser displacement sensor (optoNCDT1402, ILD1402-10, company micro-epsilon). the laser has a full duplex RS 422(two lines Tx two lines RX) to communicate with the "world" and i have no idea how to connect it with arduino board (i am using an arduino MEGA). i am a beginner with such things so i would appreciate any information.
TY
Looks like the device uses full duplex RS422 so you will probably need a couple of modules like these to convert the RS422 levels to TTL level the arduino expects. You will need two of them as the modules appear to be designed for half duplex only.
You would configure one of them for output and the other for input and connect them to one of the Serial TX/RX pin pairs.
i didnt understand what i have to connect from the sensor to this module and what from the module to arduino 
The laser displacement module (LDP) optoNCDT 1402 looks to use a full duplex connection where you have a separate transmit and receive wire pair (see attached image from manual) but the module I linked to from eBay use half duplex where a single pair of wires are used to both transmit and receive and you have to tell the module if it's transmitting or receiving on that wire pair (it cannot do both at the same time).
If you get two of these modules then you can dedicate one to transmitting and the other to receiving and get full duplex mode that the LDP expects.
The eBay modules are needed to convert the RS422 signal levels from the LDP into TTL level signals the Arduino expects and uses for serial communications.
You will also need a separate voltage supply (11-30V DC) for the LDR
