| 摘要 |
In eddy-current nondestructive testing of the surfaces of work pieces, the test apparatus comprises an eddy-current device (2) which delivers the necessary excitation signals for a probe pad (4) resting on the surface of the test piece and simultaneously processes the response signals returning from the test piece to produce an interpretable display, for example on a display screen. The eddy-current pad comprises a matrix-like arrangement of individual elements (4c) which are connected electrically via a multiplexer circuit (3) in such a way that they can be individually scanned in accordance with a timing diagram preset by a computer (1). From the timing sequence, the positional coordinate of the respective test point can be determined by the computer and processed together with the test signal to produce a surface image display (1b', 1b"). In order to prevent the probe elements influencing one another, decoupling measures are necessary. These can be implemented by means of line and column separation of the transmitting and receiving coils using diode circuitry if transmitting and receiving function are performed by the same coils or by a combination of the two. Other types of decoupling are based on the use of Hall probes or magnetic diodes in combination with transmitting coils. <IMAGE> |
