| 摘要 |
In use, the probe (1) is dropped into a ground-hole (3), for the purpose of detecting the depth of the steel casing (16) of the hole. The probe comprises a long, slim, tubular housing (2) made of stainless steel. Attached inside the housing is a springy stalk (10) made of PVC. The stalk is deflectable laterally, and carries a magnet (11) at its free end. The magnet responds to the steel, and causes the stalk to deflect while in the presence of the steel. The housing, and a stainless steel sleeve (12) around the magnet, comprise a pair of electrical contacts, which break apart and send a signal to the surface when the magnetic influence disappears. The probe is suspended on a cable (4) which is calibrated to indicate the depth of the probe when the signal is received.
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