Showing papers on "Thermal mass flow meter published in 1996"

Chemically inert flow meter within caustic fluids having non-contaminating body

Abstract: A non-contaminating flow meter having an isolation member is disclosed. The flow meter includes two pressure sensor transducers, located on opposite sides of a restriction in a conduit. Each of pressure transducers is isolated by an isolation member from exposure to fluids flowing through the conduit. The flow meter may be positioned in-line within a fluid flow circuit carrying corrosive materials, wherein the square root of the difference in pressure between the two pressure sensors is calculated to thereby determine the rate of flow within the fluid flow conduit. The flow meter compensates for changes in temperature within the fluid flow circuit and further activates an alarm if the pressure or flow rate within the fluid flow conduit exceeds or falls below a threshold level. The flow meter of the present invention also avoids the introduction of particulate, unwanted ions, or vapors into the flow circuit.

Wide range, high accuracy flow meter

Abstract: A turbine type flow meter incorporating an auxiliary turbine ahead of the main turbine, the auxiliary turbine rotating in the opposite direction from that of the main turbine and serving as a flow conditioner, thereby extending the effective range of the flow meter to lower rates of flow.

A critical evaluation of thermal mass flow meters

Abstract: Many semiconductor processes require that stable and known flows of gas be delivered to the processing chamber. The thermal mass flow meter (TMFM) is used almost exclusively in the semiconductor industry for the admission of process gases. While TMFM’s have been used in the semiconductor industry for over twenty years, much still remains to be understood about their behavior. The abundance of TMFM manufacturers that make instruments which are supposedly interchangeable complicates the use of TMFM’s because the instruments generally have different designs and performance. While some attempt has been made via written standards to address the specifications of the instruments, these standards do not address all performance issues and cannot eliminate the systematic errors in the original manufacturers calibration of the TMFM’s. Further, the TMFM’s used to measure the process gases are generally calibrated with nitrogen and ‘‘corrected’’ for other gases, but the correction factors are not well understood and ...

Fluid thermal mass flow sensor

Abstract: A fluid thermal mass flow meter including a composite flow tube having four tubular segments of high thermal conductivity formed in a length of tube made of a material having a relatively low thermal conductivity, a thin film element formed on the surface of and extending around each of the four tubular segments, circuitry for incorporating the elements into a bridge circuit, and a housing for containing the flow tube, elements, and circuitry.

Mass flow controller with vertical purifier

Abstract: A mass flow controller and purifier has a canister arranged at right angles to a flow path through the mass flow controller. The canister holds a contaminant scavenging material which a gas stream contacts as it flows to remove a contaminant such as water. A purified process gas stream is fed through a bypass of a mass flow meter. A portion of the gas is supplied to a mass flow sensor which generates a signal indicative of a rate of mass flow. The mass flow signal is amplified and the amplified mass flow signal is linearized in a linearizer. The linearized mass flow signal is fed to a comparator which compares the linearized mass flow signal with an error signal and provides an output signal indicative of a mass rate of flow through the mass flow meter. A valve is connected to the mass flow meter and is controlled by the mass flow meter signal to meter the gas.

System for measuring and controlling gas mass flow

Abstract: A system for measuring and controlling the mass flow of a gas of variable characteristics within a pipe by a metering valve, wherein a Coriolis mass flow meter mounted in the pipe is connected to the valve processor unit to calculate a correction factor for the flow rate calculated by the valve and represented by the ratio of the values originating from the Coriolis meter to those originating from the valve, this factor being updated periodically when the operating conditions do not introduce an error into the Coriolis meter. A multi-valve system for different flow rates is also described comprising a single Coriolis meter.

Air flow measuring apparatus and method thereof

Abstract: A digital signal obtained by A/D converting an output of a thermal type air flow meter is supplied along two paths. After a time constant is obtained in one path, inverse-transformation is performed to obtain an error together with an output of the other path. The inverse-transformed signal is linearized on the basis of the characteristic of the thermal type air flow meter, and a direction of flow is determined.

Calibration method of flow meters for a divided flow humidity generator

Abstract: A new calibration method of flow meters for a divided flow humidity generator is proposed. Such a generator usually has two flow meters, one for measuring air flow of the saturator and the other for measuring dry air flow for dilution. The proposed method is to introduce a third flow meter for the measurement of total flow, and by comparing the readings of these three flow meters, instrumental errors of the three flow meters are obtained by least squares calculation. The validity of the method is confirmed by calibrating the flow meters with a flow calibration system using sonic nozzles. The measured characteristics of the flow meters and the correction of humidity value of the generator are described.

Mass flow, fluid measuring and dispensing system

Abstract: A measuring and dispensing system capable of repeatedly dispensing discrete amounts of fluid having a mass of about 10 g or less and even amounts as small as 1 g. The system includes a pressurized tank for holding a fluid medium such as a liquid pharmaceutical. The tank is coupled in fluid communication to a mass flow sensor. The mass flow sensor is designed to have fluid from the tank flow through it, and measures the mass of the flowing fluid. A controller is coupled in data transmission relation to the mass flow sensor and records each measurement made by the mass flow sensor. A dispenser, such as a flexible tube, is coupled in fluid flowing relation to the mass flow sensor. A valve, such as a pinch valve, is positioned so as to be able to stop flow out of the dispenser. The valve is coupled in data transmission relation to the controller which controls opening and closing of the valve, automatically adjusting the amount of fluid permitted to flow out of the dispenser.

Axial thermal mass flowmeter

Abstract: Thermal mass flowmeter comprising a conduit defining a flow path and an elongated thermal mass flow sensor. The thermal mass flow sensor is coupled to the conduit with the longitudinal axis of the thermal mass flow sensor being aligned substantially parallel to the general direction of the fluid flow within the conduit. A method of measuring flowrates provides the same axial alignment of the thermal mass flow sensor.

Effects of Flow Pulsation on a Single-Rotor Turbine Meter

Abstract: The effects of pulsating flow on a single-rotor turbine meter with a rotor response parameter greater than unity were investigated experimentally. Oscillating velocities and pressures at various pipe cross-sections were measured which enabled characterization of flow properties at the turbine meter and their effect on meter error. Measurements confirmed that meter error depends primarily on the velocity amplitude of the flow pulsation at the rotor. Moreover, it was shown that the velocity amplitude at the rotor results from the system response, which is determined by the system geometry, pulsation frequency, flow velocity, and sound speed. Lastly, a technique was developed to determine the meter error from measurements of dynamic pressure in the pipe upstream or downstream of the turbine meter.

Method of calibrating an ultrasonic flow meter

Abstract: A method of calibrating an ultrasonic flow meter (10) first determines a static flow offset (52). Next, a dynamic flow offset (54) and a flow speed (56) are determined. An adjusted flow speed (58) is determined by subtracting the static flow offset and one half the dynamic flow offset from the flow speed to form an adjusted flow speed.

Vol. flow and density measurement device for gases and liquids

Abstract: The device has a throughflow sensor (1) operating on the effective pressure method and a throughflow sensor (3) operating on the principle of a fluid oscillator. The fluid passes through the sensors in succession and their measurement values are evaluated in a computer circuit (7). The outputs of the computer circuit are values for the vol. flow and/or the mass flow and/or the density of the fluid. The measurement range for the vol. and mass flow can be expanded by using a bypass (8). The device can have multiple scales. Its flow channels (9) can be implemented by etching or laser cutting of foil.

Air flow meter for combustion engine

Abstract: The flow meter has an air flow module (20) with an integrated flow detector (7,8) and drive circuit (10). The detector (7,8) measures the air flow in the combustion engine. The drive circuit (10) is connected to the flow detector (7,8) to output a signal corresponding to the measured air flow. An air flow measurement housing forms an air inlet (5,6) for the combustion engine. The air flow module (20) is built into the housing so that the air flow detector (7,8) can be arranged in the inlet (5,6). The housing has an end connected in flow technology to an air filter element (3). The housing also includes a tube (2) with a module fastening part connected to the other end of the housing. The cross-section of a connection section (4) between the housing and the tube (2) is perpendicular to the air flow of the smallest cross-section in the tube.

Combined water meter for large and small flow rates

Abstract: The water meter has a main meter inserted in a main flow path for large rates of flow and a secondary meter (9) inserted in a bypass line for small rates of flow, with a switching valve operated for opening the main flow path when the pressure reaches a given value. The bypass line has respective connection sections (10,11) leading to and from the secondary meter, coupled to respective chambers within the housing for the main meter. The housing has a cooperating cover (4) removed for releasing the secondary meter block (18) fitted between the connection sections.

Ozone enriched process gas

Abstract: A flow control apparatus for enriching gas containing oxygen with ozone includes a generator for producing the enriched mixture. A flow meter is connected to the generator outlet to measure the flow of the generated enriched gas. A mass flow control device is connected downstream of the flow meter. A flow control comparator compares a flow value as obtained from the measuring means and a preset constant value. A signal output of the flow control comparator is connected to a signal input of the mass flow control device for varying the mass flow in accordance with the comparison. An outlet of the mass flow control device is connected to an inlet of a compressor for compressing gas, the inlet gas pressure varying to keep compressed gas at a constant pressure. Feedback is provided between an outlet and an inlet of the compressor. A second mass control device is intermediately connected along the feedback connection for adjusting the mass flow of gas passing through the feedback means. A pressure control comparator compares the inlet pressure of the compressor to a second preset constant value. A signal output of the pressure control device is connected to a signal input of the mass flow control device for varying the mass flow being fedback in accordance with the comparison. The flow controlled compressed gas is delivered to a reactor at a constant pressure.

Experimental study on flow rate measurement by using cross-correlation of temperature fluctuations

Abstract: Flow rate measurement is one of the most important aspects of flow parameter measurements in power, petroleum and chemical industries. The applicability of cross-correlation method based on fluid temperature fluctuations to flow rate measurement under steady flow condition is investigated with experiments by using an on-line, digital instrument developed by the authors. The thermocouple transducer design, the signal data pre-processing system and the correlator design with chip microprocessor 8031 are described. The experimental results show that the intrinsic temperature fluctuations existing naturally in flowing fluid are adequate to be detected. The method is proved to be a reliable and accurate one of flow rate measurement in turbulent flow. In laminar flow, the measurement is not so satisfactory.

Transit time ultrasonic flow meters for natural gas measurement

Abstract: Transit-time ultrasonic flow meters for gas have gained a larger acceptance within the natural gas industry in recent years, and are now an option for custody transfer metering in several countries. Additionally, there are several varieties of less expensive transit-time ultrasonic flow meters which are excellent in check metering applications although limited in accuracy. The proper choice of ultrasonic flow meter normally depends on the absolute accuracy required, with the multipath configuration offering the best accuracy. Ultrasonic flow meters must be properly installed and the natural gas must be of good quality to achieve an accurate measurement, as with any type of gas flow meter. As experience grows within the measurement community, the use and applications for transit-time ultrasonic flow meters may expand greatly.

Mode recommendation in a variable displacement engine

Abstract: An apparatus for determining a number of cylinders to operate in a variable displacement engine includes a signal representative of air charge temperature, a signal representative of barometric pressure, a desired mass air flow evaluator, a maximum mass air flow evaluator, a desired exhaust gas recirculation flow evaluator, a maximum exhaust gas recirculation flow evaluator, and a controller. The controller compares the desired mass air flow to the maximum mass air flow, generating a mass air flow error signal if desired mass air flow error exceeds maximum mass air flow error. The controller also compares the desired exhaust gas recirculation flow to the maximum exhaust gas recirculation flow, generating an exhaust gas recirculation flow error signal if desired exhaust gas recirculation flow exceeds maximum exhaust gas recirculation flow. The two flow error signals are combined and compared to an acceptable error threshold, and a number of cylinders upon which to operate the variable displacement engine is recommended responsive thereto.

Two-phase flow research using the DC-9/KC-135 apparatus

Abstract: Low-gravity gas-liquid flow research can be conducted aboard the NASA Lewis Research Center DC-9 or the Johnson Space Center KC-135. Air and water solutions serve as the test liquids in cylindrical test sections with constant or variable inner diameters of approximately 2.54 cm and lengths of up to 3.0 m. Superficial velocities range from 0.1 to 1.1 m/sec for liquids and from 0.1 to 25 m/sec for air. Flow rate, differential pressure, void fraction, film thickness, wall shear stress, and acceleration data are measured and recorded at data rates of up to 1000 Hz throughout the 20-sec duration of the experiment. Flow is visualized with a high-speed video system. In addition, the apparatus has a heat-transfer capability whereby sensible heat is transferred between the test-section wall and a subcooled liquid phase so that the heat-transfer characteristics of gas-liquid two-phase flows can be determined.

Measurement of rate of gas flow using optoelectronic technique

Abstract: A simple and inexpensive device for measuring low flow rates of gas is described. Device characteristics are studied by passing air through it. A pivot system is used which undergoes deflection when air passes through the device. The deflection is measured using IR LED and photodiode combination. The photodiode output is calibrated in terms of air flow rate using a reference air flow meter. The device can be used to measure the flow rates of air up to 15 l/m. The device can also be used to measure the flow rates of gases by calibrating it with reference gas flow meter.