| 摘要 |
An instrument for determining the diameter of a hidden reinforcing bar comprises in a first embodiment a search coil (20) energised by an electrical pulse to induce eddy currents in a stainless steel bar, means (45) for alternately coupling two integrators (25, 25a) to the coil in response to two main sampling pulses which are temporally separated, to obtain a measure of the induced eddy currents at each sample pulse, means (46) for computing the ratio of integrated signals thus sampled and comparing it with a table of known ratios for standard stainless steel bar sizes. A further embodiment comprises at least one search coil (20) energised to induce eddy currents in a high tensile steel bar, means for coupling at least one integrator (25) to a search coil in response to a sampling pulse, means for computing the ratio of an integrated signal resulting from a coil placed in a first position with an integrated signal resulting from a coil placed in a second position, and means for comparing the ratio with a table of known ratios for standard high tensile steel bar sizes. |
