The structural build-up of ice presents a severe problem for helicopters when flying in super-cooled water cloud below 0°C and probes are required to provide pilot warning. The present generation of probes are accretion sensors using the growth of ice layers to measure the effect. These probes do not indicate liquid water content (LWC) above 0°C, working best in strongly icing conditions. This paper describes a new type of icing sensor which exploits the properties of positive temperature coefficient of resistance (PTCR) BaTi03 ferroelectric ceramic. The probe works equally well above and below 0°C, and possesses a short time constant (1 to 2 sec.). Hence, it is a device which can be used to give rapid warning of the entry of icing conditions as the critical region around 0°C is traversed.