Abstract: In a system for measuring the duration ratio of pulses of variable frequency, particularly in electronically controlled fuel-injection systems for internal-combustion engines, there are derived clock pulses to the frequency of which a predetermined multiple of the frequency of the pulses (input pulses) corresponds. The duration ratio is then determined by counting the clock pulses during each one pulse. For duration ratios of 0% and 100%, corresponding values are delivered independently of the counting.

Abstract: In a method for the testing of an electronic device, particularly for automotive vehicles, having a microcomputer (2), an interface as well as device inputs and outputs (connector 6), the following separate test steps are provided: In one test step at least one predetermined combination of input signals is fed into the device inputs (connector 6), and the test output signals which occur in this connection at the inputs of hardware units (4, 8, 9) of the device (1) are picked up via the interface and compared externally with the combination of the input signals. In further test steps, test control signals are fed into a single hardware unit, and the test output signals produced thereby at the output of said hardware unit are picked up via the interface for an external normal/actual comparison.

Abstract: In a method for detecting the readiness for operation of a oxygen measurement probe which is arranged in the exhaust duct of an internal combustion engine and serves together with a regulating device to regulate the preparation of the mixture for the internal combustion engine, the output voltage of the oxygen measurement probe is integrated with an integration time constant which is dependent on the internal resistance of the oxygen measurement probe. The rate of change of the output voltage is measured. Above a predetermined value of the rate of change, readiness for operation is noted. In a circuit arrangement for the carrying out of the method, there is connected to the output of the oxygen measurement probe the input of an integrator whose output is connected via an analog-to-digital converter to the input of a microcomputer. Also there can be fed to an integrator an initial value which lies in a central part of the operating range of the output voltage of the integrator.