Abstract: A method and a device for detecting rotational speed with an inductive sensor in which a sinusoidal potential is induced by a magnet wheel and then fed to a filter with a comparator connected downstream of the filter and therefrom into a square-wave signal that is essentially proportional to the rotational speed of the magnet wheel. This output signal of the comparator is evaluated in a microcomputer. In this evaluation, only the same type of edges of the comparator signal are evaluated, specifically those in which the intervals fluctuate less when considered over a certain time span. The microcomputer here can initially evaluate both types of edges, that is, positive and negative edges, and then use those edges in which smaller fluctuations, that is, interference, are determined for calculating the rotational speed. The microcomputer can also first evaluate only one type of edges and change over to edges of the other type only if the former displays interference above a present value.

Abstract: Electronic control apparatus for motor vehicles. The apparatus includes a test circuit which causes a test current to flow through a load being operated by the apparatus and which detects the magnitude of the test current. From the magnitude of the test current, an evaluation circuit determines whether the ground potential of the control apparatus and the ground potential of the load are at different levels. In response to a potential difference between the two ground potentials, the evaluation circuit initiates countermeasures for preventing damage to the electronic control apparatus, such as selectively disconnecting the load with a power switch responsive to the evaluation circuit.