| 摘要 |
<p>An inductive proximity detector includes an oscillator circuit (11) including a coil (10) to which is electromagnetically coupled a sensing coil (12) and a reference coil (13). The sensing and reference coils are connected in series in opposition with the free end of the reference coil connected to ground. The common point (14) between the coils is connected through an amplifier (15) and detector (16) to one input (17) of a differential amplifier (18). The free end of the sensing coil is connected through an amplifier (20) and detector (21) to a second input (22) of the differential amplifier (18). In the absence of an object the output from the amplifier (18) will be zero. When an object is in proximity to the sensing coil the voltages induced in the coils is no longer equal and the amplifier (18) provides an output signal which is dependent upon the proximity of the object but is independent of the magnitude of current in the coil (10).</p> |
