What You Need to Know: Measuring the Car Air Flow Meter Sensor

The mass air flow sensor is an instrument that converts the inhaled air flow into an electrical signal. The car mass air flow sensor is used to detect the intake volume of the car engine. It converts the information of the engine intake volume into an electrical signal and transmits it to the on-board computer ECU. The car mass air flow sensor is a sensor that measures the intake volume in the car intake system. The engine can calculate the amount of fuel injection based on the data value of the intake volume. Failure or damage to the car mass air flow sensor may cause unstable idle speed, poor acceleration, increased fuel consumption, high-speed powerlessness, black smoke from the exhaust pipe, and excessive exhaust emissions.

The mass air flow sensor is an instrument that converts the inhaled air flow into an electrical signal. The car mass air flow sensor is used to detect the intake volume of the car engine. It converts the information of the engine intake volume into an electrical signal and transmits it to the on-board computer ECU. The car mass air flow sensor is a sensor that measures the intake volume in the car intake system. The engine can calculate the amount of fuel injection based on the data value of the intake volume. Failure or damage to the car's mass air flow sensor may lead to unstable idle speed, poor acceleration, increased fuel consumption, powerlessness at high speed, black smoke from the exhaust pipe, and excessive exhaust emissions.

1 Mass air flow sensors are classified into two types according to the sensor signal type, including analog signal mass air flow sensors and digital signal mass air flow sensors.

Let's first look at how to measure digital signal mass air flow sensors with an oscilloscope. Connect channel one to a BNC to banana head cable, then connect a needle to the red banana head interface, connect an alligator clip to the black banana head interface, and then connect the needle to the signal line of the air flow meter sensor, and the alligator clip to the vehicle ground.

For example. BMW mass air flow sensor

Next, we set the oscilloscope, select sensor-mass air flow sensor-digital, and then click OK. For other oscilloscopes, we first set the channel to DC coupling, the probe type to voltage, the channel attenuation ratio to 1X, turn on the low pass 30KHz, the vertical gear can be set to about 5V, and turn on the amplitude, high value, low value, and frequency in the measurement item for observation. The time base can be set to about 1 second or more. When the waveform is displayed on the screen, quickly step on the accelerator, from idle to full throttle, and observe the waveform. In this way, we can watch the air flow meter movement from idle to acceleration and back to idle on one screen. Pay special attention to the oscilloscope waveform and measurement value at the driving ability failure speed.

For example. Mazda 6 mass air flow sensor + throttle position sensor

For analog signal flow meters, the vane type is used here to illustrate. The vane type mass air flow sensor is characterized by integrating the functions of fuel pump control switch, air temperature sensor, CO regulator and mass air flow sensor. The structure is more complex, but the accuracy is higher. Its working principle is to let air flow into the engine, through the measuring unit, and flow through the spring-loaded blade. The movement of the blade is proportional to the amount of air entering the engine. The movement of the air blade is recorded by the sliding arm sliding on the carbon track. The voltage output of the sliding arm is reported to the electronic control module (ECM), and then the ECM delivers the correct amount of fuel according to the measured air flow. The common wire connections for this type of mass air flow sensor are four-wire, five-wire and seven-wire.

The connection method is similar to the previous one:

Connect a BNC to banana head cable to channel 1 of the oscilloscope. Connect an alligator clip to the black connector of the banana head cable. Connect a stinger to the red connector of the banana head cable. Connect the alligator clip to the negative terminal of the battery. Ground the stinger and connect it to the signal output of the mass air flow sensor. When the waveform is displayed on the screen, step on the accelerator and observe the waveform from idle to full throttle.

The hot wire mass air flow sensor is a heating wire evenly distributed in the metering channel. The sensor uses a platinum wire as the hot wire resistor and the thermistor for detecting the ambient temperature, which is installed in the intake duct detection area. The hot wire generates heat when it is energized. When the airflow passes through the hot wire, the heat of the hot wire is cooled. Controlling the current on the hot wire can keep the temperature on the hot wire constant. In this way, the control current has a corresponding proportional relationship with the intake volume, that is, the airflow can change the output voltage of the mass air flow sensor. The output signals of the hot wire mass air flow sensors produced by various automobile factories are slightly different.

Hot wire air flow meters are both analog and digital. The difference is that the digital type outputs a digital signal while the analog type outputs a voltage signal, which can be used directly without computer conversion. Usually, the frequency of a digital air flow meter increases as the air flow increases.

Jiangxi Getai Auto Parts Co., Ltd. uses a hot wire air flow meter, which is made based on the principle of heat dissipation. It has a simple structure, no mechanical rotating parts, is durable, has high precision, and can accurately measure the amount of air. However, since the hot wire is very thin and exposed to the air, sand in the air can easily break the hot wire when the air flows at high speed. For details, please contact our customer service and enter the website: en.getaimaf.com.