Airflow Sensor

Rajkumar Sharma
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Tested
SKU: EL143531
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This airflow sensor consists of INA326 precision instrument amplifier, double 100uA REF200 current sources, and a REF3025 2.5V reference voltage chip. Airflow dynamics dictate how much the voltage will increase or decrease for a given airflow rate. Therefore, the relationship between temperature and flow rate would have to be established for a method such as this to be useable. Two IN4148 diodes are used to sense the temperature, Diode D3 should be in static air and Diode D2 should be installed in the airpath flow path. The circuit works with 5V_DC and draws a few mA of current. REF3025 provides an accurate reference voltage which is 2.5V. Temperature linearity is within a tenth of a degree. The airflow is correlated to the change in D2 voltage. D2’s junction temperature and voltage are related to the airflow. D2 and D3 should be in the same temperature environment.

Features

Power Supply: 5V DC
Diode Junction Temperature: 0 – 70Degree
Output: 1V to 1.75V (1.25 @ 27 Degree Centigrade)
PCB Dimensions: 45.40 x 11.91 mm
2 x 3 mm Mounting Holes

Connections

CN1: Pin 1 = VCC, Pin 2 = GND, Pin 3 = GND, Pin 4 = Output
D2: Air Flow Path Temperature Sensor
D3: Static Air Temperature Sensor
D1: Power LED

Schematic

Parts List

NO.	QNTY.	REF.	DESC	MANUFACTURER	SUPPLIER	SUPPLIER PART NO
1	1	CN1	4 PIN MALE HEADER PITCH 2.54MM	WURTH	DIGIKEY	732-5317-ND
2	4	C1,C2,C3,C5	100nF/50V CERAMIC SMD SIZE 0805	MURATA/YAGEO	DIGIKEY
3	1	C4	10uF/10V CERAMIC SMD SIZE 0805	MURATA/YAGEO	DIGIKEY
4	1	C6	500PF/50V CERAMIC SMD SIZE 0805	MURATA/YAGEO	DIGIKEY
5	1	D1	LED RED SMD SIZE 0805	OSRAM	DIGIKEY	475-1278-1-ND
6	2	D2,D3	1N4148	ON SEMI	DIGIKEY	1N4148FS-ND
7	2	R1,R3	1K 5% SMD SIZE 0805	MURATA/YAGEO	DIGIKEY
8	1	R2	50K 1% SMD SIZE 0805	MURATA/YAGEO	DIGIKEY
9	2	R4,R5	200K 1% SMD SIZE 0805	MURATA/YAGEO	DIGIKEY
10	1	U1	REF200	TI	DIGIKEY	296-44855-5-ND
11	1	U2	INA326	TI	DIGIKEY	296-15312-1-ND
12	1	U3	REF3025	TI	DIGIKEY	REF3025AIDBZTCT-ND