Abstract: Reduced attitude sensitivity is achieved in a fluid mass flow meter of the type which determines fluid flow from the temperature difference between an upstream sensor and a downstream sensor positioned along the flow path of the fluid externally of a sensing conduit for the fluid. A housing, taking particular forms, has wall structure spaced along the sensors adapted to substantially limit the ambient gaseous atmosphere along the sensors to a thin film. The housing wall structure further is spaced along portions of the sensing conduit between the sensors and the input and output ports of the conduit to substantially limit the ambient gaseous atmosphere along such portions to a thin film. In one form, such wall structure, along these portions, converges from both directions along the conduit, to provide support regions for the conduit. The sensors, specifically, are self-heating coil elements formed of temperature-sensitive resistance wire wound around the outside of the sensing conduit.

Abstract: A flow dividing structure for a mass flow controller includes a base having a main passage which includes an upsream circular passage, a downstream circular passage, and a tapering circular passage which connects the upstream and downstream circular passages. A plug inserted in the main passage includes a first cylindrical portion, a second cylindrical portion and a tapering frustoconical portion. A first annular passage is defined between the first cylindrical portion and the inner circumferential surface of the upstream circular passage. A second annular passage is defined between the second cylindrical portion and the inner circumferential surface of the downstream circular passage. A tapering annular passage is defined between the tapering frustoconical portion and the inner circumferential surface of the tapering circular passage. A flow measuring passage bypasses the tapering circular passage and connects the upstream circular passage with the downstream circular passage.

Abstract: A frusto-conical adjustable laminar flow bypass restrictor which is disposed within a conically tapering bore to form a conduit capable of maintaining laminar flow and adjustable to form annuli of varying thicknesses to allow proper sensor calibration over a wide range of flow rates.

Abstract: A tubular furnace, such as a diffusion furnace, having a temperature controlled central region bounded by end walls heated to the temperature of the central region, at least one of said end walls being movable to and from the outer edge of said central region. By means of a temperature-sensing feed-back circuit, the entire temperature controlled region can be maintained at a predetermined isothermal condition, or a temperature gradient can be maintained by heating one of the end walls to a specified higher temperature and heating the other to a specified lower temperature. A combustor, for example for an exothermic chemical reaction, can be located within a guard heater adjacent one of the end walls.

Abstract: A pair of mass flow sensors are used to separately monitor the mass flow rates of a carrier gas and of a mixture of carrier gas and source vapor formed a mixing station. The rates are compared, for example by substracting the carrier gas flow rate from the mixture flow rate, to generate a signal representing the mass flow rate of the source vapor. Flow of the carrier gas to the mixing station is modulated in accordance with the difference between this signal and a command signal representing a predetermined flow rate. The system can be calibrated by flowing the carrier gas alone through both sensors, by passing the mixing station, and adjusting the signal for one or both sensors so that the signals from both sensors are equalized.

Abstract: A cross-flow reactor for single pass reaction of a plurality of semiconductor wafers with process gas at spaced locations within a heated reactor chamber. The process gas flows along a heated length of the chamber, counterflows to at least three spaced locations within the chamber, traverses the longitudinal axis of the chamber at the spaced locations and then exhausts from the chamber. In a particular embodiment, two or more different process gases are delivered as separate streams to the spaced locations for convergent cross-flowing thereat.

Abstract: A mass flow sensor system for measuring the flow rate of a fluid in a sensing tube at diverse angular attitudes. Output signal distortion is minimized by neutralizing the effects of convection forces. The sensing tube is formed as a by-pass coupled to a fluid conduit and includes a loop in the shape of a single-turn helix. Circulation of the fluid through the loop cancels gravity-induced convection forces caused by temperature gradients and significantly reduces sensitivity to attitude change. Heating and temperature-sensing resistor coils are wound around the outer surface of the looped portion of the tube. The heater increases the tube temperature above that of the entering fluid, and the temperature difference between the temperature sensors, corresponding to rate of mass flow, is detected as a voltage output signal generated in an associated bridge circuit.

Abstract: A mass flow sensor system for measuring the flow rate of a fluid in a sensing tube at diverse angular attitudes. Output signal distortion is minimized by neutralizing the effects of convection forces. The sensing tube is formed as a by-pass coupled to a fluid conduit and includes a loop in the shape of a single-turn helix. Circulation of the fluid through the loop cancels gravity-induced convection forces caused by temperature gradients and significantly reduces sensitivity to attitude change. A center-tapped temperature-sensitive resistor coil is wound around the outer surface of the loop. The coil is heated, and the temperature differential between the ends of the coil, corresponding to rate of mass flow, is detected as a voltage output signal generated in an associated bridge circuit.

Abstract: Accurate and stable measurement of the dielectric constant of a substance or a mixture of substances is achieved by the use of an oscillatory system incorporating a shorted transmission line as a delay means, to cycle the system. The substance for which the dielectric constant is to be determined is introduced between or about the elements of the transmission line so as to vary the propagation rate or delay of signals through the transmission line. Accordingly, the frequency of oscillation for the system is indicative of the dielectric constant of the substance. Several specific forms of transmission lines, embodied as sensors are disclosed along with different forms of oscillator drivers.

Abstract: Apparatus and method for obtaining a controlled gas mixture of predetermined proportionality using a temperature dependent permeation tube or like source for the addition of a small amount of a constituent gas in a higher flow rate carrier gas. A thermistor having a negative coefficient of resistance is associated with the permeation source and electrically connected to a flow controller for the carrier gas to automatically regulate the flow rate of the carrier gas in accordance with temperature variation of the permeation source.

Abstract: A mass flow meter for measuring the flow rate of a fluid in a sensing tube over a wide ambient temperature range and with low sensitivity to attitude change. A pair of sensor temperature sensitive resistive wire coils are wound around the outer surface of the tube along the flow path of the fluid and are encased in open cell foam material. The sensor elements are heated and the rate of mass flow of the fluid is directly proportional to the temperature differential between the sensor elements. The sensor elements can be connected to a bridge circuit for detecting the temperature differential of the sensor elements. Tilting the sensor from the initial balance position results in a change in meter reading of less than 0.5%.

Abstract: A flowmeter in which a laminar flow conduit is connected in parallel to a flow restrictor comprising at least one disk having an opening through opposite surfaces and at least one conduit from the opening to the perimeter of the disk, each conduit having an effective length to diameter ratio sufficient to assure laminar fluid flow.