Niveauschalter

摘要

In the level switch, the inverting input of an operational amplifier (1) with positive and negative feedback is connected to a ring plate (rp) and its noninverting input is connected to an electrode (4) and its output to earth via a capacitor (5). A counterelectrode (oe) connected to earth surrounds one end of a dielectric body (db) of a probe (s4), into which a ring plate (rp) is coaxially installed at its other end, and at the circumference of the body (db) between the counterelectrode (oe) and the ring plate (rp), a shield electrode (se) is arranged which is connected to the output of the operational amplifier (1) via a capacitor (6). The other end of the body (db) is terminated by the electrode (e). The output of the operational amplifier (1) is connected to the output (o) of the level switch via a band-pass filter (7) with a low frequency, a rectifier (8), an amplitude limiter (9) and an amplifier (10) which are connected in series.