Automobile Camshaft Position Sensor Signal Measurement and Waveform Analysis - Oscilloscope

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Automobile Camshaft Position Sensor Signal Measurement and Waveform Analysis - Oscilloscope [Copy link]

The camshaft position sensor is also called the camshaft angle sensor, phase sensor, cylinder identification sensor, and some cars also call it the 1 cylinder top dead center sensor. The most common name for modern cars is the camshaft position sensor.

The main function of the camshaft position sensor is to detect the camshaft position and rotation angle, thereby determining the compression top dead center position of the first cylinder piston. At startup, the engine ECU identifies the position and stroke of each cylinder piston based on the signals provided by the camshaft position sensor and crankshaft position sensor, controls the fuel injection sequence and ignition sequence, and performs accurate fuel injection and ignition control.

Camshaft position sensors can be commonly divided into Hall type, induction type, and AC excitation type.

Below we take the example of using an oscilloscope to measure the signal of a Hall-type camshaft position sensor.

First, connect a BNC to banana head cable to channel 1 of the oscilloscope, then connect an alligator clip to the black banana head, clamp it to the negative pole of the battery for grounding, and connect a needle to the red banana head. Hall-type camshaft position sensors usually have three wires, a positive power line, a ground line, and a signal line. Insert the needle into the signal line.

The oscilloscope channel attenuation ratio is set to 1X, the time base is set to about 50ms, and the vertical scale can be set to 1V/div or 2V/div

The waveform of the Hall-type camshaft position sensor may vary in amplitude and it is more important to detect its signal frequency rather than the voltage value.

As shown in the waveform below, measured by the oscilloscope cursor, X1 is 1ms, X2 is -155ms, and observing the waveform repetition pattern, it can be seen that the position of the waveform from X1 to X2 is a cycle of the waveform, and its value is measured as Delta 156ms, so the frequency is the reciprocal of the cycle, which is 6.41Hz. Observe that the vertical scale of the oscilloscope is 2V/div, so one grid in the vertical direction represents a 2V voltage value. The waveform occupies about 6 grids in the vertical direction, so the signal voltage peak is about 12V.

For Hall sensors, there are two principles for observing waveforms. One is to pay attention to whether the baseline of the signal is normal, and the other is to see whether the highest point of the signal is within the manufacturer's set range.