| 摘要 |
Four electromagnets are connected in a Wheatstone bridge configuration, two of the electromagnets having their magnetic circuit open and the other two having their magnetic circuits closed, A moving armature (15) connected to the moving member, is placed at a controlled distance from the ends of the open magnetic circuit. An electronic detector and alarm circuit are connected at the sensor terminals of the Wheatstone bridge. - A threshold detector (20) which compares the signal from the bridge to a reference signal, operates an output relay if an excessive error appears. The reference signal and the bridge sensitivity may be adjusted. A timer circuit is also incorporated.
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