HIP-100 is an acoustic sensor developed as an add-on option to the OWI-series Weather Sensors, giving an even greater range of weather data collection. It is difficult to discriminate a solid ice particle from a water droplet using optical techniques alone. When an ice particle hits a metal surface, the noise caused by the impact is clearly distinguishable from the impact of a water droplet. Based on this effect, We have developed and patented an acoustic technology to detect the ice pellets and hail stones: HIP-100. Combining the optical and acoustic signal, reliable detection and discrimination of ice particles can be achieved. No other present weather sensor can distinguish hail and ice pellets as well as the OWI sensor with the HIP-100.