008345 Issue 1 AWM40000 SERIES Airflow Sensors, Ampliefi d, and Unampliefi d The small size and thermal isolation of DESCRIPTION the microbridge mass airflow sensor The AWM40000 Series Airflow Sensors are responsible for the extremely fast are based on proven microbridge response and high sensitivity to flows. technology and include both Dual Wheatstone bridges control airflow unamplified sensor-only devices and measurementone provides closed loop amplified signal conditioned devices. heater control, the other contains the The microbridge mass airflow sensor dual sensing elements. operates on the theory of heat transfer. The heater circuit minimizes shift due Mass airflow is directed across the to ambient temperature changes by surface of the sensing elements. Output providing an output proportional to voltage varies in proportion to the mass mass flow. The circuit keeps the heater air or other gas flow through the inlet temperature at a constant differential and outlet ports of the package. (160C) above ambient air temperature This sensor has a unique silicon chip which is sensed by a heat-sunk resistor based on advanced microstructure on the chip. The ratiometric voltage technology. It consists of a thin film, output of the device corresponds to FEATURES thermally-isolated bridge structure the differential voltage across the Precision silicon micromachining containing heater, and temperature Wheatstone bridge circuit. Sensitivity to low flows (0.1 SCCM to sensing elements. The bridge structure 6 SLPM) The unamplified versions require both provides a sensitive and fast response to Adaptable for use with higher flows the heater control circuit (Fig. 2) and the the flow of air or other gas over the chip. Low power consumption allows for sensing bridge supply circuit (Fig. 3) for Dual sensing elements positioned on use in portable devices and battery- operation per specification. These two both sides of a central heating element powered applications circuits are not on board the sensor and indicate flow direction as well as flow Analog output must be supplied in the application. The rate. Standard 2,54 mm 0.10 in mounting differential amplifier circuitry (Fig. 4) The specially-designed housing centers may be useful in providing output gain precisely directs and controls the airflow Laser-trimmed interchangeability and/or introducing voltage offsets to the across the microstructure sensing Accurate sensing of low pressure sensor output (Fig. 5). element. Mechanical design of the The amplified versions can be used package allows it to be easily mounted to increase output gain and introduce to printed circuit boards. voltage offsets. The circuits shown in Laser-trimmed, thick film and thin To view the entire mass Figs. 2, 3, and 4 are all provided onboard. film resistors provide consistent airflow product portfolio, interchangeability from one device to click here. POTENTIAL APPLICATIONS the next. The microbridge mass airflow Medical sensor uses temperature sensitive - Respirators and ventilators resistors deposited within a thin film of - Oxygen concentrators and silicon nitride. They are suspended in conservers the form of two bridges over an etched - Anesthesia machines cavity in the silicon. Industrial - HVAC damper control The chip is located in a precisely - Gas analyzers dimensioned airflow channel to provide - Low vacuum control a repeatable flow response. Highly - Process control effective, thermal isolation for the heater - Leak detection equipment and sensing resistors is attained by - Vent hoods etching the cavity space beneath the - Gas metering flow sensor bridges. - Chromatography AIRFLOW SENSORS, AMPLIFIED, AND UNAMPLIFIED AWM40000 SERIES TABLE 1. SPECIFICATIONS UNAMPLIFIED AMPLIFIED CHARACTERISTIC AWM42150VH AWM42300V AWM43300V AWM43600V-2 1 Flow range (full scale) 30 SCCM 1000 SCCM +1000 SCCM 0 SLPM to 6 SLPM Calibration gas nitrogen nitrogen Recommended excitation voltage 10 0.01 Vdc 10 0.01 Vdc 10.000 0.010 Vdc 10.000 0.010 Vdc Power supply: minimum 8.0 Vdc 8.0 Vdc 8.000 Vdc 10.000 Vdc maximum 15.0 Vdc 15.0 Vdc 15.000 Vdc 15.000 Vdc Power consumption 30 mW typ. 30 mW typ. 60 mW max. 75 mW max. 8.5 Vdc 1.5 mVdc at 55.2 Vdc 2.0 mVdc at 5 Vdc 0.15 Vdc at 5 Vdc 0.15 Vdc at Output at laser trim point 25 SCCM 1000 SCCM 1000 SCCM 6 SLPM Null output 0 mV 1 mV 0.0 mVdc 1.5 mVdc 1.0 mVdc 0.05 mVdc 1.000 Vdc 0.050 Vdc Null output shift (-25C to 85C) 0.20 mVdc 0.20 mVdc 0.025 Vdc max. 50 mVdc max. Output voltage shift: 25C to -25C +2.5% reading max. +2.5% reading,max. -5.0% reading max. -7.0% reading max. 25C to 85C -2.5% reading max. -2.5% reading max. +6.0% reading max. +7.0% reading max. 1 Repeatability and hysteresis 0.35% FSO typ. 0.50% reading typ. 0.5% reading max. 1.00% reading max. Pressure drop at full scale 0.008 inH 0 typ. 1.02 inH 0 typ. 1.02 inH 0 typ. 8 inH 0 typ. 2 2 2 2 1.0 ms typ. 1.0 ms typ. 1.0 ms nom. 2 Response time 1.0 ms nom. 3.0 ms max. 3.0 ms max. 3.0 ms max. Overpressure 17.2 bar 250 psi max. 10.3 bar 150 psi 10.3 bar 150 psi 1.7 bar 25 psi Maximum flow pulse to 5 SLPM/s 5 SLPM/s 5 SLPM/s 5 SLPM/s prevent damage Output load: NPN (sinking) 10 mA 10 mA 10 mA 10 mA source, 20 mA typ. PNP (sourcing) 20 mA 20 mA 20 mA -25C to 85C -25C to 85C -25C to 85C -25C to 85C Operating temperature range -13F to 185F -13F to 185F -13F to 185F -13F to 185F -40C to 125C -40C to 125C -40C to 90C -40C to 125C Storage temperature range -40F to 251F -40F to 251F -40F to 194F -40F to 251F Ratiometricity error 0.30% reading 0.3% reading 0.3% reading nom. 0.8% reading max. Shock (5 drops, 6 axes) 100 g peak 100 g peak 100 g peak 100 g peak 3 Weight 17.5 g 0.62 oz 11 g 0.39 oz 1 Output voltage is ratiometric to supply voltage. 2 Repeatability and hysteresis tolerances reflect inherent inaccuracies of the measurement equipment. 3 Includes 4.3 g for backing plate. 2 Sensing and Internet of Things