Abstract: A device for measuring and monitoring the volume of liquid in a container comprises an adapter for mounting the device in an opening in the top wall of the container. The adapter supports a beam onto which one end of a float is connected such that the free end of the float extends substantially vertically into the container. A strain gauge is disposed on the beam so that the measuring direction of the gauge is parallel to the main axis of the beam. The device can also include a sensor for measuring physical parameters of the container. A processor is connected to the strain gauge and any sensor to take data from those input devices. During a calibration operation, a measurement function is derived to correlate strain gauge readings to the volume of liquid in the container. The function is recorded in a processor which takes data from the strain gauge and calculates the actual volume of liquid in the container. An output component displays the measurement.