| 摘要 |
PURPOSE:To achieve a highly accurate and economic detection of surface flaws in broad material to be detected by providing a frequency control section and a switching control section for controlling a plurality of excitation frequencies at an excitation section and a program section for storing a plurality of detection coils into any of frequencies in a signal processing circuit. CONSTITUTION:An output signal of a switching control section 2 is inputted into a program section 27 which sorts coils in 15 channels are sorted with a pin connection in such a manner that three blocks come down to any of three frequencies for example in a 1 block-channel array. An output signal of the program section 27 is inputted into a frequency control section 28. The frequency control section 28 outputs three kinds of VCO voltages in a time series according to output signals of the program section 27. A VCO voltage as output of the frequency control section are inputted into an excitation section 1. Another output signal of the frequency control section 28 is inputted switch sections 7, 12 and 21 at points B, C and E and according to programmed frequencies of the coils any one of the switches at the point B, C or E is turned ON to select among filter sections 8, 8' and 8'' and phase detecting sections 10, 10' and 10'' which were adjusted for each of three kinds of frequencies. |
