| 摘要 |
The thread (F) is passed through a capacitive sensor (12) which generates a sensor signal in accordance with the changes in the capacitance of the sensor (12). The zero level of the sensor signal can drift due to contamination of the sensor. To allow a reliable absolute-value measurement independent of interruptions of the measurement during the cleaning of the sensor heads, the device is equipped with a compensation arrangement (20) which is used for generating any compensation signal and for combining the signal with the sensor signal to form a composite measurement signal (20a). The compensation arrangement comprises a zero-level control arrangement which switches on when the thread (F) is removed from the sensor (12) in order to return the level of the composite measurement signal (20a) to a particular nominal value independent of the degree of contamination of the sensor. <IMAGE> |
