High reliability Semiconductor back-pressure sensor used at the sensing section. No mechanical moving parts to wear out means higher reliability. No need to adjust Simply set the length of the tube to an arbitrary length and preparations are complete. The end of the tube becomes the sensing point. An orifice is built into the unit for supplying 20±1kPa gas. Once the gas is supplied,it will automatically become the purge flow. When the liquid level reaches the end of the tube an alarm will be displayed.