This video show daruifuno online ORP sensor ASR400 and ASR401. The difference between the two sensors are the measuring range: ±1500mV and ±2000mV. The shell material is PPS, can use in high temperature and corrosion-resistance. The ORP probe electrode is widely used for drinking water, sewage, wastewater. If you want to know more about the ORP sensor , feel free to contact us.