Working principle of MAF

Air flow sensor, also known as air flowmeter, is one of the important sensors of EFI engine. It converts the air flow into electrical signal and sends it to the electronic control unit (ECU). As one of the basic signals to determine the fuel injection, it is a sensor to measure the air flow of the engine. With the use of microcomputer to control fuel injection, several other air flow sensors have appeared, such as valve type air flow sensor and Karman vortex air flow sensor.

According to the different characteristics of air flow sensors, the fuel control system is divided into L-type control with direct measurement and D-type control with indirect measurement. The biggest advantage of the air flow sensor is that the instrument coefficient is not affected by the physical properties of the measurement medium, so it can be extended from one typical medium to other media. However, due to the great difference in the velocity range of liquid and gas, the frequency range is also very different.

The function of automobile air flow meter is to monitor the amount of engine air intake, and convert the air intake information into electrical signal and transmit it to the electronic control unit (ECU). The ECU determines the fuel injection quantity of the engine through this signal. The symptoms of automobile air flow meter failure or damage include unstable idle speed, poor acceleration, increased fuel consumption, weak high speed, black smoke from exhaust pipe, excessive exhaust emission, etc.

The abnormal air flow sensor will not cause the engine to start, but it will affect the dynamic performance of the engine. Air flow meter damage is often due to the air filter is not replaced for a long time or the use of poor quality air filter, resulting in the air flow meter hot wire dust accumulation time is too long, resulting in inaccurate change of resistance value or failure, dust will also lead to the throttle valve is too dirty.

In order to obtain the best concentration of mixture under various operating conditions, the air flow meter must correctly measure the air intake into the engine at each moment, which is the main basis for ECU to calculate and control the fuel injection quantity of the engine. If the sensor or circuit fails, the ECU will not get the correct air intake signal, and it will not be able to control the fuel injection quantity normally. The mixture will be too rich or too thin, and the engine will not run normally.

For precision thermal gas mass flowmeter:
1. 780i pipeline type can reach ± 0.5% Rd (flow rate ≥ 50% FS); 640i plug-in type can reach ± 0.75% Rd (flow rate ≥ 50% FS) [original s series ± 1% FS]

2. The repeatability reached ± 0.15% FS [original s series ± 0.2% FS]

3. Measurement range: for air, the maximum measurable mass flow rate reaches an astonishing 300nm / s [the original s series can measure the maximum 100nm / s for air, and the larger the measurement will affect the accuracy]

4. Three variable measurement and output: gas mass flow rate, gas temperature and gas pressure (two standard configurations, VT and VTP) [the original s series only measures mass flow]

5. QuadraTherm ™ The S-Series is designed to separate only two parts of the sensor

6. iTherm ™ The brain manages the switching of gas species, the measurement of temperature, pressure, and heat conduction caused by external temperature

7. DrySense ™ : zero drift dry sensor technology ensures long-term accuracy and lifetime warranty

8. Dial-A-Pipe Gamma : the pipe size and material can be customized on site (the roughness of the inner wall of the pipe affects the measurement accuracy)

9. Dial-A-Gas ™ : it can customize the type of gas on site and build in abundant gas related parameters to realize field switching

10. iTherm Gamma Internal gas database: 18 kinds of gases and mixtures, which can be imported through the network in the future, are still being updated

11.ValidCal ™ : field calibration, because the dry sensor technology has ensured that the probe will not drift, so as long as the actual flow is simulated by software, the analog-to-digital conversion output part in the calibration meter can be verified. [upgraded version of original s series SIP verification]

12. Smart interface program: intelligent software [upgraded version of original S-Series SIP software]

13. All kinds of bus: Hart, MODBUS, foundation fieldbus, PROFIBUS DP