| 摘要 |
<p>Self-adjusting capacitive level switch for a non-contact or contact sensing of media or objects comprising a sensor (S6), on a dielectric body (db) of which between an opposite plate (op) and a plate (p) a screening plate (sp) is mounted. Starting from the plate (p) there are alternately mounted additional screening plates (sp1, ..., spn+1) connected through a resistor (r1) to the screening plate (sp) and additional plates (p1, ..., pn). Groups of additional plates (p1, ..., pn+1) are connected through resistors to the inverting input of an operational amplifier (1). At the beginning of each oscillation half-period the potential of the plates (p, p1, ..., pn) has a phase opposite to the phase of the screening plates (sp, sp1, ..., spn+1). The level switch detects electrically very poorly conductive materials with the relative permittivity near to 1 even through a thick, electrically well conductive deposit on its sensor.</p> |
