A contactless method of measuring a foundry mould filling degree in course of its pouring with liquid metal is suggested. The concept is based on infrared radiation of molten metal appearing in venting and flow-off holes. As the detector, an infrared channel receiving diode is applied. Three solutions were tested. In the first solution, the diode is placed at the calculated distance from the radiation source, in a housing that suppresses the scattered signal. The housing contains the electronics, while power supply and control signals are delivered by conductors. A diode actuation threshold is established in order to obtain high resolution and repeatability of the results. On the output, a miniature relay transmits the signal to the control system. In the second solution, the measuring system is supplied with a battery and the signal in transmitted through a plastic optical fibre. In the third solution, the optical fibre serves as an energy carrier. The optical system focuses the infrared radiation and introduces the energy to the optical fibre. On the other end of the fibre, a phototransistor amplifies the signal, forms it and transmits to the control system. Some experiments were carried out. Their results permitted noting disadvantages and advantages of individual solutions. It was evidenced that the measurement results obtained using the infrared radiation are independent on a constructional design. The solutions utilising optical fibres proved to be more useful in industrial conditions. Targets and further directions of research works using transceivers for wireless data transmission are presented.