| 摘要 |
<p>Apparatus is described for corrosion detection, especially detection of corroded wall ties. An array of Hall effect sensors (10) is linked by the magnetic field of a permanent magnet and the output from the sensors are multiplied by devices (30, 32, 34, 36, 44) and amplified by amplifier (42) to drive a meter supply (46). The patterns of voltages generated within the array of sensors differ between the situation where the field of the permanent magnet is substantially undisturbed, where it is disturbed by the presence of a sound wall tie, and where it is disturbed to a lesser extent by the presence of a corroded tie, due to the reduced ferrous content of a corroded tie. In a method of detecting corroded wall ties, a unit having the array of Hall effect sensors and the permanent magnet is positioned adjacent a wall with the magnet more remote from the wall than the sensors and the unit is moved to a wall position at which the sensors exhibit a voltage pattern, and a reference signal is generated by processing the sensor voltage. The unit is then moved to a position at which the sensors exhibit a different voltage pattern and the sensor voltages are again processed to establish a measurement signal, and the reference signal and measurement signal are compared.</p> |
