Abstract: A wire wound resistor is vertically disposed in a vessel. The resistor has a former of between 20 mm and 45 mm diameter and resistance wire of a resistance of between 1 and 4 ohms per turn connected in the circuit of an A.C. bridge circuit. Impedance change is indicated on a display unit calibrated to indicate the change in level of liquid e.g. milk in the vessel. The resistance wire is laid on the former by applying ultrasonic sound energy to soften the former which is of polysulfone or polycarbonate and the wire embedded in the softened former material. The vessel is shaped at the lower end to assist in giving linear readings when the level of liquid is low.

Abstract: A wire wound resistor is vertically disposed in a vessel. The resistor has a former of between 20 mm and 45 mm diameter and resistance wire of a resistance of between 1 and 4 ohms per turn connected in the circuit of an A.C. bridge-circuit. Impedance change is indicated on a display unit calibrated to indicate the change in level of liquid e.g. milk in the vessel. The resistance wire is laid on the former by applying ultrasonic sound energy to soften the former which is of polysulfone or polycarbonate and the wire embedded in the softened former material. The vessel is shaped at the lower end to assist in giving linear readings when the level of liquid is low.