The well-head pulley guides the camera probe with the cable down to the well, vertically, smoothly.
Installed with a digital depth counter, when the cable moving down,the depth counter will measure the meters it have passed, and transfer the information into digital signal, and them combined with the OSD mode, at last, show the detph information in the monitor screen.
The process is real time synchronous, we could inspect the camera image with its depth information.
Accuracy of the depth counter is up to 0.05m, and support zeroed and calibration.