A micro refinery produces ethanol that is distilled in a distillation tube. A sensor detects the liquid level within the distillation tube. The sensor includes a guide wire mounted within the distillation tube, a float mounted around the guide wire and an external magnetometer circuit mounted to an external surface of the distillation tube. The float includes a magnet and as the float rests on the upper surface of the fluid in the distillation tube, the external magnetometer circuit detects the position of the float and provides information about the liquid level in the distillation tube.