| 摘要 |
Two monostable time switching stages (1, 2) are connected with a level setting capacitor (Cp) and the measurement probe (Cs) as time-determining capacitances and are triggered periodically, at a rhythm of 300 kHz, by a repeater stage (8). Connected to the two time switching stages is a subtraction stage (3) which triggers a retriggerable monostable multivibrator (6) as long as the probe capacitance (Cs) is less than that of the level setting capacitor (Cp). If the probe capacitance is greater than that of the level setting capacitor, the multivibrator (6) is no longer triggered and, when it returns to its stable state, triggers an alarm (9, 10) via an AND gate (5). A failure indication, which consists of an AND gate (4) (which is connected to the two time switching stages) and a further retriggerable monostable multivibrator (7), likewise triggers the alarm (9, 10), via the AND gate (5), if the time switching stages (1, 2) fail or the repeater stage (8) fails. <IMAGE>
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