interactive catalog replaces catalog pages sensing and control honeywell inc. 11 west spring street freeport, illinois 61032 honeywell sensing and control has replaced the pdf product catalog with the new interactive catalog . the interactive catalog is a power search tool that makes it easier to find product information. it includes more installation, application, and technical information than ever before. these pdf files are no longer being updated and will be removed by january 2001. click this icon to try the new interactive catalog.
airflow sensors awm series microbridge mass airflow 64 honeywell 1 micro switch sensing and control 1 1-800-537-6945 usa 1f 1-815-235-6847 international 1 1-800-737-3360 canada awm 1000/2000/3000 series awm 40000 series awm 5000 series features 1 state-of-the-art silicon micromachining 1 sensitive to low flows 0.1 sccm to 20 slpm 1 adaptable for use with higher flows (see application note 2 page 128.) 1 fast response time 1 analog output 1 low power consumption 1 repeatable response 1 laser-trimmed interchangeability 1 accurate, cost effective flow sensing 1 in-line printed circuit board terminals 1 standard 0.100 n (2,54mm) mounting centers 1 accurate sensing of low pressure 0.001 n to 4.0 n h 2 o (.003 to 10mbar) operation the microbridge mass airflow sensor op- erates on the theory of heat transfer. mass airflow is directed across the surface of the sensing elements. output voltage va- ries in proportion to the mass air or other gas flow through the inlet and outlet ports of the package. the specially designed housing precisely directs and controls the airflow across the microstructure sense element. mechanical design of the package allows it to be easily mounted to printed circuit boards. the microbridge mass airflow sensor has a unique silicon chip based on advanced microstructure technology. it consists of a thin-film, thermally isolated bridge structure containing heater and temper- ature sensing elements. the bridge struc- ture provides a sensitive and fast re- sponse to the flow of air or other gas over the chip. dual sensing elements posi- tioned on both sides of a central heating element indicate flow direction as well as flow rate. laser trimmed thick film and thin film resistors provide consistent inter- changeability from one device to the next. the microbridge mass airflow sensor us- es temperature-sensitive resistors de- posited within a thin film of silicon nitride. they are suspended in the form of two bridges over an etched cavity in the sil- icon, shown below. the chip is located in a precisely dimensioned airflow channel to provide a repeatable flow response. highly effective thermal isolation for the heater and sensing resistors is attained by etching the cavity space beneath the flow sensor bridges. the small size and thermal isolation of the microbridge mass airflow sensor are responsible for the ex- tremely fast response and high sensitivity to flows. dual wheatstone bridges control airflow measurement e one provides closed loop heater control, the other contains the dual sensing elements. the heater circuit minimizes shift due to ambient temper- ature changes by providing an output proportional to mass flow. the circuit keeps the heater temperature at a con- stant differential (160 c) above ambient air temperature which is sensed by a heat-sunk resistor on the chip. the ratio- metric voltage output of the device corre- sponds to the differential voltage across the wheatstone bridge circuit. applications 1 damper control for heating, ventilation, and air conditioning systems 1 gas analyzers 1 low vacuum control 1 process control 1 medical respirators and ventilators 1 oxygen concentrators 1 leak detection equipment 1 vent hoods 1 anesthesia control 1 gas metering 1 gas chromatography notice dust contamination may be possible in some applications, the effects of which can be minimized. by design, dust parti- cles that may be present in the air stream will flow past the chip parallel to the chip surface. in addition, the micros- tructure chip produces a thermophoret- ic effect, which repels micrometer-sized dust particles away from the bridge structure. dust adherence to chip edges and channel surfaces can be prevented us- ing a simple filter. a disposable five- micron filter used in series on the up- stream side of the airflow device will provide adequate filtering in most appli- cations. for a list of possible filter sourc- es, see filter manufacturers, page 126. caution product damage awm series microbridge mass airflow sensors are not designed to sense liquid flow and will be damaged by liquid flow through the sensor.
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