The 1150C Heated Pressure-Based Mass Flow Controller using viscous flow through a choked orifice is a pressure-based measurement and control system designed to meter and control vapor from low vapor pressure liquid and solid sources directly, without the need of a carrier gas. The 1150C consists of a fixed flow element and one capacitance manometer for flow measurement, with a proportioning solenoid control valve for flow control (U.S. Patent No. 4,679,585). The 1150C is contained within a compact temperature-controlled assembly with a temperature status LED and relay to indicate when temperature is in range. The 1150C Heated Pressure-Based Mass Flow Controller using viscous flow through a choked orifice is capable of delivering vaporized liquid source materials such as: TEOS, DADBS, HMDS, TMCTS, TEAL, TEB, TEG, TEI, TMAL, TMB, TMG, TMI, TaCl5, DMEAA, It[OCH(CH3)2]4, TiCl4, TIBAL, and TMP.