| 摘要 |
The indicator produces voltage, and involves two poles to which leads of electrically conductive material are connected at the primary ends. The first of the leads has its other end connected to earth, whilst the second lead has its other end coupled to the reinforcement of the building component. Thus, the poles are in electrical contact with each other, forming a closed circuit. - Alternating voltage is fed to the electrical circuit with a positive mean value during a number of recurrently selected primary time intervals with intermediate secondary intervals. The polarity of the poles can be changed during the alternating effect of positive and negative pulses of predetermined length. A component is available to regulate and control the positive and negative pulse lengths, and a further control regulates the primary and secondary time intervals. |
