| 摘要 |
A sensor which determines an operational variable of a system, for example an oxygen sensor of an internal combustion engine, generates a usable output voltage only at the proper elevated temperature. In order to uncouple the control loop from an improperly operating sensor, i.e., a cold sensor, the internal resistance of the sensor is monitored by passing through it a test current and by comparing the resulting voltage drop to a set-point value. Whenever the internal resistance is too high, indicating non-readiness, the control loop is opened and a substitute average output value is supplied to the fuel injection system or to the system driven by the control loop. During normal operation, the sensor is tested periodically with short test pulses to continuously monitor the operational readiness, but the main test current is normally shut off, thereby preventing falsification of the output signal. |
