Liquid Level Indicator is a standard feature on liquid filled transformer tanks, since the liquid medium is critical for cooling and insulation. This indicator is typically a round-faced gauge on the side of the tank, with a float and float arm that moves a dial pointer as the liquid level changes. It usually gives an audible or vibratory indication when a conducting fluid has reached a pre-set height. It is used to determine the volume content of liquid in vessels such as underground fuel.