Mass Flow Controllerthat Semicon Can t Touch
At about one-third the size of standard mass flow controllers, the MicroFlo (right) was designed as a "lowest-cost" unit with outstanding performance and reliability. Fully configurable by the customer, the controller offers dual-calibration capability (two gases, two flow ranges, or both), creating two MFCs in one. ... The MediFlo, intended for higher flow rates, has all the capabilities of the MicroFlo. ... The MediFlo operates off a single supply, consumes <2 W of power, and is designed for low-pressure high-flow applications. The term semiconductor grade refers to the ability of a mass flow controller (MFC) to handle the highly corrosive gases used in semiconductor manufacturing. To meet this design constraint, MFC manufacturers must use high-purity stainless steel to isolate the flow sensor elements and incorporate complex geometries to achieve acceptable flow sensitivity. Called “bypass” technology (see the sidebar, “Take the Bypass”), it is an ideal solution for semicon and became the “standard” sensing technology in the MFC industry. ... 2002 Sensors - January 2002 - A Mass Flow Controller that Semicon Can’t Touch Seite2 Photo 1. ... The thermal mass of the sensor is so small that it responds to flow changes in milliseconds while canceling common-mode errors. ... The sensor consists of a flow channel and three active elements: a single heating element centered between two thin film resistive thermal detectors (RTDs). The microstructure is suspended in a solitary flow tube and positioned directly in the flow stream. ... The fundamental advantage of the inline sensor is its direct integration into the flow stream and its infinitesimal thermal mass. The thermal mass of the heating element and the two RTDs is so minuscule, and the RTDs are so close to each other, that flow rate sensitivity is maximized and common-mode errors cancel.