Abstract: An autonomous apparatus for measuring the amount in volume, weight or level of a liquid in a tank. The invention provides an easy to read digital numerical display in what ever units the user has calibrated it for, indicating the amount of fluid in the tank. The self-contained electronic devise is normally mounted to a pipe nipple on the top of an above ground storage tank. An attached displacement device extends down through the pipe nipple into the liquid to sense the level of the liquid. This device relies on ambient light to power the solar cells and recharge a battery, which provides all the necessary power to operate the device both day and night. The apparatus is designed to be intrinsically safe and totally sealed. As such it operates electrically as a stand alone gauge and is intended as a general purpose indicator of tank contents for any tank location.