an ice detector has a pair of probes , each of which is used for determining the accretion of ice thereon . one of the probes in the assembly is configured so the smaller droplets of supercoooled water are inertially separated and flow away from the one probe . the ice accretion on the one probe is primarily from large supercooled droplets . the ice accreting on the one probe is therefore biased to supercooled large droplets . the probes are connected to detection circuitry that will determine the ratio of the rates of icing between the probes so the presence of supercooled large droplets can be determined . in one form , a flow guide is arranged to create an airflow that carries smaller droplets past one of the probes without impinging on the probe , but the higher inertia , supercooled large droplets will impinge on that one probe .