| 摘要 |
Test signals are generated by a microcontroller (i.e., micro) and coupled to a transistor which is in series with an inductive sensor of a wheel speed sensor input circuit to test the input circuit. In one test, a test signal from the micro sweeps through a range of predetermined frequencies to turn the transistor off and on to provide a simulated wheel speed signal which is used to compute a corresponding number of simulated wheel speeds. The programmed micro compares the simulated wheel speeds with the predetermined frequencies to determine if the various components of the circuit are operating properly and also to determine if the wheel speed arithmetic of the programmed micro is operating properly since actual wheel speed routines within the micro are used to compute the simulated wheel speeds. In another test, a low pass filter circuit coupled to an A to D input port of the micro are both tested by having the micro read the input port at various times before and after a second test signal from the micro is coupled to the transistor.
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