SIGNAL PROCESSING APPARATUS FOR DETECTING FLAW USING EDDY CURRENT

PURPOSE:To evaluate the damage of the heat transfer pipe of a heat exchanger without errors, by comparing signals from an eddy current flaw detector, and obtaining an AND value of the result of comparison. CONSTITUTION:A flaw detecting piece 2 is connected to an eddy current flaw detector 1, which generates four kinds of flaw detecting signals. The flaw detecting piece 2 is inserted into a heat transfer pipe 4 of a heat exchanger, which is a body to be checked, and moved in the pipe. The signals from the flaw detector 1 are combined and supplied to a signal operating unit 5. The effects of a pipe plate 3a and a supporting plate 3b of the heat transfer pipe 4 are removed in three signal operators 51-53. Then, the output signals from the unit 5 are inputted into a comparing and judging unit 6, which is provided with seven comparators 61a-61c, 62a, 62b, 63a and 63b. The signals are compared with each preset value and judged. The signals, which are outputted from the comparators of the unit 6, are inputted into an discriminating gate unit 7, in which AND gates and NAND gates are combined. Logic operations are performed, and the flaws and the attached materials of the heat transfer pipe 4, which is overlapped with the pipe plates 3a and the supporting plate 3b, are identified. Therefore, the accurate, quick judgment can be performed. Since the AND value of the result of the evaluation of a plurality of the signals is obtained, evaluation without errors can be performed.