An apparatus for monitoring a height of liquid in a liquid storage tank is provided, the apparatus includes a first rotatable element rotatable in response to a change of a liquid level in a liquid storage tank and including a first magnetic component having a first magnetic field, and a second rotatable element rotatable in response to the rotation of the first rotatable element and including a second magnetic component having a second magnetic field. The apparatus further includes a sensor assembly which includes a first sensor component located within range of the first magnetic field and structured to be effective in providing a first signal indicative of a position of the first magnetic component, and a second sensor component located within range of the second magnetic field and structured to be effective in providing a second signal indicative of a position of the second magnetic component. The apparatus further includes a data transmitter/microprocessor assembly in electronic communication with the sensor assembly and structured to be effective in receiving the first and second signals from the first and second sensor components, respectively, and processing said first and second signals into data representing a height of liquid in a liquid storage tank.