Abstract: A turbine wheel flow measuring transducer located in a fluid receiving chamber is provided for measuring low flow rates of fluids, whether liquids, gases, or mixtures, and in controlling the fluid flow rates. The transducer is in the form of a small diameter turbine wheel having a plurality of semi-circular lateral openings in its outer periphery. The openings are sequentially presented to the incoming fluid into the chamber and the turbine wheel rotates according to the fluid flow rate. Measuring and controlling of fluid flow rates as low as 4-5 milliliters per minute and as high as 100 milliliters per minute is permitted.

Abstract: A flow system includes a proportional valve constructed of chemically inert materials (PTFE) to produce variable fluid flow rates of liquids including inert, and high purity, and even highly corrosive liquids. Gases of many varieties can also be flow controlled. The valve may be precisely set, either manually, or by use of an actuating motor, remotely or electronically, for various flow rates for the required fluid. The valve allows for specific proportional flow parameters to be programmed into valve structure and configuration to provide precise and repeatable highest resolution flow control for a wide variety of complex flow conditions (pressure, temperature and viscosity).

Abstract: The flow of a fluid at low flow rates is measured in a flow sensing assembly and controlled without introducing measuring devices into the fluid flow path. The flow sensing assembly is enclosed in a housing to lessen ambient and fluid temperature change effects on the measurements obtained. As the fluid is flowing through tubing in the flow sensing assembly, the tubing is heated to impart heat to the fluid. Heat sensors are attached at spaced positions from each other along the tubing in the direction of fluid flow to sense temperatures. The amount of heat applied to the tubing is controlled to maintain an established temperature differential between the heat sensors. The amount of heat applied is measured to provide an accurate and proportional indication of the fluid flow rate.

Abstract: The flow of a fluid at low flow rates is measured and controlled without introducing measuring devices into the fluid flow path. As the fluid is flowing through tubing, the tubing is heated to impart heat to the fluid. Heat sensors are attached at spaced positions from each other along the tubing in the direction of fluid flow to sense temperatures. The amount of heat applied to the tubing is controlled to maintain an established temperature differential between the heat sensors. The amount of heat applied is measured to provide an accurate and proportional indication of the fluid flow rate.

Abstract: A calibration system for a tube prover used in gas flow rate calibration equipment includes a low friction piston which provides an effective seal without the use of mercury. The low friction piston is easily movable in a prover tube of the calibration system in response to gas flow rates, even low flow rates. The piston is constructed of a light weight, low friction fluorinated hydrocarbon material. The piston has first and second seals which provide a positive seal with the inner surface of the prover tube and which maintain the alignment of the piston within the prover tube.

Abstract: A sensing circuit of a thermal mass flow sensor provides enhanced precision control of heating and temperature sensing coils used for fast sensing responses. The sensing circuit includes a pair of coil servo loops achieving servo loop control of the sensing coils in each servo loop. The current paths in the servo loop include a main current path carrying low levels of current and minor current paths carrying very small levels of current. These small levels of current have insignificant current levels compared to the levels of current in the main current path. The single main current path in the servo loop allows nearly all of the current from the primary servo amplifier to be used for driving the coils, thereby improving the efficiency of the coil servo loop. The heating and sensing coil in each servo loop is coupled to an integration network for measuring power provided to the coil.

Abstract: A laminar flow element for use in thermal mass flow sensors and flow controllers is designed to provide a high degree of precision. The precision laminar flow element includes a laminar flow element having a generally pointed entry end for maintaining a pure laminar flow path around the laminar flow element. The generally pointed entry end serves to direct an incoming gas flow stream equally about an outer surface of the laminar flow element. In this way, the laminar flow path is uniform so as to maintain a desired flow accuracy. The laminar flow element provides a plurality of standoff pins protruding from the outer surface of the laminar flow element to maintain a substantially equal radial clearance around the outer surface. By maintaining a substantially equal radial clearance from one laminar flow element to another, the laminar flow element is highly interchangeable.

Abstract: A sensing circuit of a thermal mass flow sensor provides enhanced precision control of heating and temperature sensing coils used for fast sensing responses. The sensing circuit includes a pair of coil servo loops achieving servo loop control of the sensing coils in each servo loop. The current paths in the servo loop include a main current path carrying low levels of current and minor current paths carrying very small levels of current. These small levels of current have insignificant current levels compared to the levels of current in the main current path. The single main current path in the servo loop allows nearly all of the current from the primary servo amplifier to be used for driving the coils, thereby improving the efficiency of the coil servo loop. The heating and sensing coil in each servo loop is coupled to an integration network for measuring power provided to the coil.

Abstract: A turbine wheel flow measuring transducer is provided for measuring low flow rates of corrosive fluids, whether fluids or gases. The transducer has a turbine wheel rotating in a housing fluid chamber at a rate set by the corrosive fluid flowing through the housing. Infrared light passing through the fluid is sensed and converted by an optical flow measurement circuit. The amount of light which passes through a rotating turbine wheel indicates flow rate. A processing circuit forms output signals indicative of fluid flow rate.

Abstract: A turbine wheel flow measuring transducer is provided for measuring low flow rates of corrosive fluids, whether fluids or gases. The transducer has a turbine wheel rotating in a housing fluid chamber at a rate set by the corrosive fluid flowing through the housing. Infrared light from an optical flow measurement circuit passes through spaced holes in the rotating turbine wheel. The amount of light which passes through the wheel indicates flow rate. The housing is made from a corrosion resistant synthetic resin which is also translucent to infrared light from the light source. The light source thus need not be in the housing fluid chamber, materially simplifying the transducer. Further, the turbine wheel is provided with an improved bearing support so that problems of thermal expansion of the housing are overcome.