AWM2000

The AWM2000 has the following features including State-of-the-art silicon micromachining;Sensitive to low flows-0.1 sccm to 20 LPM;Adaptable for use with higher flows;Fast response time;Analog output;Low power consumption;Repeatable response;Laser-trimmed interchangeability;Accurate, low cost sensing;In-line printed circuit board terminals.

The AWM2000 series microbridge mass airflow sensor is a passive device comprised oftwo Wheatstone bridges: onefor closed loop heater control, and one for the twin sensing elements. Figures 1 and 2 indicate the additional circuitry necessary for proper operation of the sensor.The heater control circuit in Figure 1 is required for operation per specification. It is uniquely adapted to the flow sensor and provides an output proportional to mass flow by minimizing errors due to ambient temperature changes. The circuit is designed to keep the heater temperature at a constant differential above ambient air temperature under varying temperature and air flow. Ambient temperature is sensed by a similar heatsunk resistor on the chip.

The microbridge mass airflow sensor operates on the theory of heat transfer due to mass airflow directed across the surface of the sensing element. Output voltage varies in proportion to the mass air or other gas flow through the inlet and outlet ports of the package.The microbridge mass airflow sensor has a unique silicon chip based on recent advances in microstructure technology. It consists of a thin-film, thermally isolated bridge structure containing heater and temperature  sensing  elements.  The bridge structure provides a sensitive and fast response to the flow of air or other gas over the chip. Dual sensing elements tlanking a central heating element allow the indication of direction of flow as well as rate of flow. Laser trimmed thick film and thin film resistors result in consistent sensitivity from one device to the next.A specially designed housing precisely directs and controls the airflow across the sensing microstructure. It is easily mounted to printed circuit boards.