| 摘要 |
A caliper for measuring tree diameters of trees. A slide having a permanent magnet is movable along a graduated rule, the caliper including a pair of legs, one leg attached to one end of the rule, and another leg attached to the slide. An electronic unit measures the position of the slide along the rule and stores measurement values and other desired data. A wire extends within a longitudinal internal cavity in the rule and co-acts with a piezo crystal adjacent an end of the caliper. The wire is connected to a pulse generator that generates short electric pulses of predetermined duration. The caliper also includes a detector that co-acts with the piezo crystal and with the pulse generator pulses to detect a geometric change in the wire that is sensed by the piezo crystal, which emits an electrical pulse in response to that geometric change. |
