| 摘要 |
<p>A proximity monitor for movement at a selected distance from a surface includes: a first microwave sensor (23) having an antenna pattern (24) directed toward the surface (21), the principal component of the pattern parallel to the surface being in the direction of the movement (22); a second microwave sensor (25) having a second antenna pattern (26) directed toward the surface (21), the principal component of the second pattern parallel to the surface being at a direction opposite to that of the movement (22), and the patterns being mutually spaced at the surface in the direction of movement; a magnetic anomaly sensor (27) giving an output representative of the presence at the surface of a magnetic anomaly located between the patterns; and circuit means (31 - 63) connected to the sensors (23, 25, 27) for performing a control function when the signals from the sensors are above pre-determined levels in a pre- determined time relationship.</p> |
