Showing papers on "Thermal mass flow meter published in 1982"

Monolithic integrated direction-sensitive flow sensor

Abstract: A manolithic integrated direction-sensitive flow sensor for measuring the velocity of gas or liquid flow is described. Its operation is based on the transfer of heat from a heated chip to a flowing fluid. Temperature differences on the chip are a measure for the flow velocity and flow direction in a plane parallel with the chip's surface. The sensor can be embedded in a wall, for example, in a wall of a tube conducting a fluid flow, and can be shielded from a direct contact with the fluid. Measurements are stated for velocities in a range below 3 m/s for air at room temperature.

Thermal pulse time-of-flight liquid flow meter

Abstract: A novel method uses no orifices or moving parts but rather dual glass-encapsulated thermistor probes to impart a heat pulse into the flowing liquid and to detect its arrival down-stream. Detection triggers a subsequent upstream thermal pulse and the cycle repeats. The time of flight of the warmed zone is thus inversely related to liquid flow and the digital output is inherently computer compatible. A key to achieving dependable operation is electronic double time differentiation of sensor output to reject characteristically slower ambient thermal drift and to minimize response time in preparation for subsequent pulse detection. The meter is capable of measuring liquid flow rates between 0.1 and 10.0 cm/sup 3//min with a precision of at least 0.1% (sigma). The flow cell's glass and inert plastic composition makes it highly corrosion resistant. Besides its general utility in flow metering, this method is especially well suited to high performance liquid chromatography applications. 6 figures, 1 table.

Mass flow controller apparatus

Abstract: An apparatus capable of selecting and controlling the mass flow rate of a gas to be substantially constant over extended periods of time at very low flow rates and very low gas partial pressures is disclosed.

A calibration system for calorimetric mass flow devices

Abstract: Describes a simple gas flows calibration system which consists of the combination of a secondary standard mass flowmeter and a primary standard volume displacement method. The system has been built for the routine calibration of calorimetric mass flow devices as well as for changing their flow range. Reviews the literature on thermal mass flow instruments and discuss the operations of a commercial shunt type mass flow controller. In the appendix the authors derive the pertinent equations for the different calorimetric mass flow devices in detail. They review a few of the more common calibration methods used in industry and give the corresponding equation and flow corrections required.

Method and apparatus for calibrating flow meters

Abstract: The specification discloses a method and apparatus for calibrating liquid flow meters of all types. The system includes a scale for dynamically determining the weight of a liquid flowing through a flow meter, together with means for measuring the flow through the flow meter being tested. In the case of a glass tube flow meter, a float detection system is used, whereby the operator will set the flow through the flow meter to a desired point, use the float detection system to make certain the float stays in a fixed position during the test, as well as to locate the float from a reference point, and use the system to measure the flow through the flow meter during a fixed period of time, thereby obtaining a reading, in engineering units, for each predetermined position of the float.

Flow meter including improved laminar flow restrictor device therefor

Abstract: This disclosure relates to a flow meter having an improved flow restrictor for creating laminar flow in the flow meter. The improved flow restrictor is an adjustable bypass or flow restrictor which comprises a stack of alternate slotted discs and non-slotted, smaller diameter, washers with a diameter of 80% of the slotted discs, to form a plurality of micro-channels 0.09 mm square and 3 mm long which is a length to area ratio sufficient to assure laminar fluid flow through the flow meter.

Method and apparatus for measuring fluid flow rates and volumes through fluid flow paths

Abstract: A system for measuring and for monitoring pulsed and steady state fluid flow through fluid flow paths includes a device for modifying the temperature of part of the flow path and a device for pyroelectrically detecting changes in temperature as fluid flows through the temperature-modified part of the flow path.

Compound liquid flow meter with fast crossover characteristic

Abstract: This compound flow meter includes a high capacity meter and a low capacity meter connected in parallel with it. The flow through the high capacity meter is controlled by a main valve subject to the pressure difference across the meter and biased closed by a spring. The flow through the low capacity meter is controlled by an auxiliary valve. Mounted on the main valve is a means responsive to the pressure difference across it and moving in the same direction as the main valve in response to that pressure difference. That pressure difference responsive means operates a piston which is aligned with the auxiliary valve, so that the operation of the auxiliary valve is determined by the sum of the movements of the main valve and the pressure difference responsive means.

Apparatus for measuring the mass of a pulsating medium flowing in a flow cross-section

Abstract: An apparatus for measuring the mass of a pulsating medium flowing in a flow cross-section, in particular for measuring the aspirated air mass of internal combustion engines. The apparatus includes a temperature-dependent measuring resistor, whose temperature and/or resistance is regulated in accordance with the mass of a flowing medium. The measurement signal (U S ) representing the mass of the medium can be influenced in accordance with the flow direction by use of a pressure-sensing element which has corresponding electrical contacts and when there is a flow reversal the pressure-sensing element, via a correction circuit, suppresses the delivery of the measurement signal (U S ) to an electronic control unit. By use of the correction circuit it is also possible to subtract the amount measured during a reverse flow from the measurement signal made during flow in the desired flow direction. As a result, an error in the measurement signal (U S ) during pulsating flow is prevented.

A meter for measuring quantities of heat and use of this meter.

Abstract: A heat quantity meter for measuring the quantity of heat abstracted from a circulating flow of liquid by a consumption unit based upon the indirect measurement of the volume flow rate of the liquid, while maintaining a sub heat flow from and/or to the main heat flow transported by the flow of liquid, the volume flow rate of the flow of liquid being determined on the basis of the flow rate dependant heat transfer in the boundary layer of the flow liquid at the location of the sub heat flow, by determining the temperature differential across the boundary layer and the sub heat flow passing through said boundary layer, comprising a conduit section (26) for the supply flow of liquid (24), possibly a conduit section (27) for the drain flow of liquid (25), a thermal connection (3) to at least one of said conduit sections to obtain the sub heat flow, at least one temperature sensor (22,23) on the supply conduit section or/and the drain conduit section and two additional temperature sensors (20,21) on the thermal connection on either side of the heat resstance thereof to determine the quotient of the temperature differential across the fixed heat resistance of the thermal connection and the temperature differential across the boundary layer. The thermal connection and the measuring bodies of the temperature sensors being of easily heat conducting material are taken up in a housing (30) through thermal insulation means (28,29,37,43) having in its entirety such an implementation that a linearized and reproduceable relation is obtained between the said quotient of temperature differentials and the volume flow rate.

Bell-Vol High Volume Sampler

Abstract: Maintenance of a constant flow rate has been a long-standing problem with hi-vol samplers used to collect ambient aerosol. Numerous types of commercially available flow controllers are currently in use. A passive flow controller has now been developed that operates without external power or electrical circuits, and, when coupled with an AC inductive motor and cyclone blower, effectively controls flow rate between 100 and 1500 L/min. The flow controller described here controls mass flow rate rather than motor speed - the method used in commercially available hot wire anemometer electronic flow controllers - by continuously applying pressure to the outlet air stream. Thus, the controller is unaffected by such problems as brush wear and line voltage variations that are common to hi-vol samplers. In operation, the pressure drop across any constant flow resistance, such as an orifice, elbow, or length of tubing in conjunction with a diaphragm, functions as a servo mechanism to maintain a constant drop...