Air Flow Sensor HH-MAF1207

HEHUA NO.: HH-MAF1207

OEM NO.: 
22680-AD210

APPLICATION:
NISSAN MAXIMA QX II 2.0，2.5，3.0 (1999/04-2003/11)

mass air flow (MAF) sensor responds to the amount of air flowing through a chamber containing the sensor. It is intended to be insensitive to the density of the air.
The sensor for volume consumption of air is used in many systems for management of engines for measuring value of the transitory cost of air. Air consumption is one of the basic parameters for calculating the necessary amount of fuel. MAF usually is placed after the air filter and before the throttle valve in the air flow sucked into the engine.

Types of sensors
According to the principle of operation are:

With analog output signal. Sensor’s output signal voltage depends on the air consumption – VAF and Hot Wire sensors.
With a digital output. Sensor’s output signal frequency or duty cycle depends on the air consumption – HFM sensors.
Depending on the type of construction:

A sensor which measures the volume (l / h) of the air flow – Vane Meter Sensor (VAF and also known as LMM).
A sensor which measures the mass (kg/h) of the air flow – Hot Wire MAF sensor (also known as HLM).
A sensor which measures the mass (kg/h) of the air flow – Hot Film MAF (HFM).
Nowadays the most common are MAF, because they don’t have mechanical moving parts and have great performance and accuracy. This type of sensor is not sensitive to the pulsations associated with opening and closing of intake valves and the output reading does not depend on the density of incoming air.

Working principle of the MAF sensor
MAF sensor which measures the mass of air flow – Hot Wire sensor
Sensor of this type is shown in fig. 3. Hot wire (2) with diameter of 70μm is mounted in a measuring tube located before the throttle valve.
Operation of MAF is based on the principle of constant temperature. Heated platinum wire, suspended in the engine’s air stream (3), is one of the legs of a Wheatstone bridge. Constant temperature of approximately 100 ºС is maintained by increasing or decreasing the electrical current flowing through the circuit while the incoming airflow cools the wire.