| 摘要 |
<p>The present invention relates to a physical quantity sensor provided with an overvoltage protection, in particular an underground water level sensor intended for placing into a borehole (2)¿of an earth body (1). The sensor is disposed in a common metal casing (4) along with the overvoltage protection (7), which includes at least one lightning arrester (71) representing the first stage of at least two-stage overvoltage protection (7) the second stage of which is represented by at least one varistor (72) and/or at least one transil (74). The metal casing (4) representing a common ground of the sensor and the overvoltage protection (7) has a maximum potential difference between the casing (4) and operating conductors (61, 62) of the sensor given by a protective level of the overvoltage protection (7) with respect to ground that is determined by the second, optionally further stage of the overvoltage protection (7).</p> |
