X-Rite i1Display Pro Plus - Advanced Measurement and Care; Monitor Measurement Technique; Ambient Light Measurement

To mount the device on your display, position the optics in contact with the center of your display. Then position the USB cable and counterweight behind your display.
Monitor measurement 4
Adjust the position of the counterweight according to the size of your display. Be sure the foam pad on the front of the device sits flat on your display.
Ambient light measurement