Detection of Vacuum Bellows Intake manifold Absolute-pressure Sensor

1. Structure and operating principle:

Driven by vacuum bellows, the inductor-variable intake absolute-pressure sensor is mainly composed of bellows, core, induction coil, and electronic circuit bellows. It is welded by a thin metal sheet. Its interior is pumped into a vacuum, and the exterior connected with the intake is manifold. The change of external pressure will cause the expansion and contraction of it. There is a linkage between the core and bellow placed inside induction coil. The induction coil is composed of two windings, one of which is connected with the oscillating circuit generates AC voltage, generates a magnetic field around the coil, and the other is induction winding, which generates a signal voltage. When the intake manifold pressure changes, the bellow drives the core to move in the magnetic field, which changes the signal voltage generated by the induction coil. After detection, shaping, and amplification by an electronic circuit, the signal voltage is sent to ECU as the output signal of the sensor.

2. Detection of Voltage Value of Sensor Output Signal:

Because absolute pressure transducer (used in the early Bosch D-Jetronic system) uses a 12V power supply to complete the voltage conversion, it is impossible to check the sensor's quality by unplugging the socket. During the detection, the multimeter (voltage) of the probe are respectively inserted into the wire connector contact with two terminals, measuring the output voltage. The measurement method is as follows: Close the ignition switch (ON) without socket, and contact the multimeter pen with Vs and E terminals. The voltage value is about 1.5V when the vacuum pipeline is opened and the atmospheric pressure is added. When the vacuum pipeline is sucked by the mouth, the voltage value should change from 1.5V to the direction of decrease. When the engine idles, the voltage value is about 0.4V, while the engine speed increases, the voltage value increases.
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