| 摘要 |
<p>The invention concerns a type 4 - 20 milliamperes or 0 - 20 milliamperes current loop, connecting an analog sensor (1) to an acquisition system (3) traversed respectively by a sensor current (lc) and an acquisition current (la). A test circuit is mounted parallel to the current loop for injecting into said current loop a superposition current (Is) which is superposed to the sensor (lc) or acquisition current (la). In a first embodiment, a variable voltage (V4) generator (7) injects the superposition current (ls) by addition to the acquisition current (la), thereby controlling a low current threshold of the acquisition system (3). In a second embodiment, a variable current regulator injects the superposition current (Is) by addition to the sensor current (lc) thereby controlling a high current threshold of the acquisition system. The acquisition system low and high threshold test is carried out without opening the current loop.</p> |
