Air flow metering

Fig. 7.1 Experimental set up for sonochemical carbonization experiments [24] (1) Ultrasound Probe, (2) C02 gas sparger, (3) Conductivity meter, (4) pH meter, (5) C02 gas cylinder, (6) C02 gas flow meter, (7) Air flow meter, ( ) Air compressor (9) Magnetic stirrer, (10) Ca(OH)2 slurry...

Datametrics Model lOOVT Air Flow Meter. Measurements were taken at various locations above the soil or water surface at a height of 0.8 cm, where the laminar air flow velocity was greatest. Depending on the probe location relative to the air dispersion tube, the measured wind speed varied from 0.5 to 1.5 m/s, with an average of 1 m/s. At greater heights above the surface, the air flow rate was much lower and the air flow patterns were unknown. 

Air-flow metering is used in gasoline and diesel engines. In passenger cars more than 50% use air-flow metering engine displacement has a wide range of 1-6 L. 

For metering air mass various physical principles can be used. The first automotive application in 1972 used a vane type air-flow meter [1], The signal from a vane meter has to be corrected for air density variations, so the thermal measurement principle was chosen for the next generation of air-flow meters. 

The present state-of-the-art is to use a thin-film sensor for thermal air-flow meters. The thin film is deposited on a planar or cylindrical substrate. A planar substrate allows for resistor structures, which make complex measurement tasks possible, for example back-flow detection. By exploiting microsilicon technology the resistors can be located on a thin diaphragm, which results in very short response times. 

Fig. 7.6.3 Function principle of the Bosch mass air-flow meter.

Fig. 7.6.4 Back-flow detection with the microsilicon sensor element. Comparison of the in dicated air mass of a microsilicon and of a hot-wire air-flow meter. The microsilicon airflow meter indicates the back flow that appears periodically...

For an air-flow meter the package plays a decisive role with respect to the measurement task. One aspect is that the package for an air-flow meter is determined... 

The necessary function blocks for an air-flow meter are the following. 

The Bosch microsilicon air-flow meter is available with analog (HFM5) or digital (HFM6) signal evaluation circuits. 

Fig. 7.6.9 Electric function blocks of the Bosch air-flow meter (analog design)...

Fig. 7.6.10 Signal path of the analog design air-flow meter...

The calibration of the air-flow meter HFM5 is performed with the following steps (Fig. 7.6.10). 

The temperature signal, which is needed for optimum temperature compensation of the air-flow meter, is available as an additional signal and can be used for engine control purposes. 

Fig. 7.6.12 Metering duct for air-flow meters showing different types of flow straighteners...

An overview of thermal air-flow meters is given here. Examples of microsilicon sensor elements and requirements for the packaging of air-flow meters are presented. Also different possibilities for signal formation are described. Finally it is shown that the good dynamics inherent to microsilicon sensor elements can be combined with robustness increasing measures that allow the air-flow meter to operate under severe environmental conditions. 

In commercial systems the accuracy of instruments such as fuel and air flow meters is frequently poor due to the type of meter, placement of the meter, initial setup (mol.wt., temperature range, pressure, etc.), or even as the result of erroneous scaling factors. Attempts made to try to determine what instrument or if an instrument is in error by making mass and energy balance calculations are also usually not productive since all of the necessary parameters are usually not available to close a mass and energy balance around the system. For example, waste gas flow volumes are often not measured since they may contain aerosols, solids, or tar-like constituents that can plug or coat flow mefers causing them to fail or to have poor accuracy. 

Wu Y, et al. 1992. The design and analysis of an imp roved high air flow meter with analog/digital filters. IEEE Transactions on Instrumentation cuid Measurement, 41(6) 791 796. 

Lead code][Wireless substations address code] [Relay station address code] [Superior relay station address code] [Air-flow meter code][Air volume] [CRC check code]... 

Lead code and CRC check code are automatically added by nRF905, wireless substation address code is 2 bytes which is the primary address location when distinguish the working area and the wind speed is abnormal Air-flow meter code is 4 bytes, and it is only corresponding to the number of the wind member, and it can ensure the source of the air monitoring data The superior relay station address code is used to control process that data transfers in wireless communication subnet. Air volume is defined as an integer that is 3 bytes, and the second byte is decimal point. 

Coaxial air flow and air dynamically driven devices are supplied by Nisco AG. Biichi Labortechnik also supplies an innovative nozzle that enables the use of encapsulators as an air flow system instead of a vibrating nozzle system, which can be an advantage for encapsulation of clusters or large particles. A coaxial air flow or air-driven systan must be equipped with a pump or mechanism to feed the polymer to the nozzle and two connections, the first to deliver the polymer and the second, which is concentric to the first, to deliver the air stream. The air stream is controlled by an air flow meter and a stirred gelling bath is mandatory to keep the beads separated from each other and avoid coalescence. 

Process air temperature too low Incorrect temperature setting on-controller Controller malfunctioning Process heating elements Thermostat malfunction Voltage differentials Inadequate air flow Hose connections incorrect Inadequate insulation Dryer inadequate for required temperatures Reset for correct temperature Check electrical connections. Replace/repair if needed Check electrical connections Replace/repair if needed Replace or repair Check supply voltage Check/clean filters, check blower rotation and correct, check and repair air flow meter Check connections. Delivery hose should enter hopper at bottom Insulate hopper and hopper inelt air line Replace with high temperature dryer... 

Dew point reading could be good but resin is still wet.) Blower rotation incorrect Air ducts blocked Air flow meter incorrect Desiccant bed contaminated Tightly packed material in hopper Check manufacturer s electrical instructions, and change blower rotation Remove obstruction Disengage line exiting dryer repair if needed Replace desiccant (see Note 3) Increase hopper size or drain hopper and refill... 

Fan shrouds, radiator parts, air flow meter o HVAC components in Talc-filled PP... 

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