Abstract: A circuit for the rapid calculation of the real and imaginary parts of the h first harmonics of a signal supplied by a measuring device and particularly for the analysis of the voltage supplied by a non-destructive eddy current testing probe. The circuit comprises an analog-digital converter, a random access memory, and calculating means comprising a PROM, a counter, a multiplier, an accumulator and a sequencer.

Abstract: Eddy current non-destructive testing device comprising in per se known manner an exciting generator, a probe connected to the latter, means for sampling in the probe a measuring voltage, means for producing a reference voltage, a differential amplifier having a first and second input and an output, a first input receiving the measuring voltage and the second the reference voltage, digital signal processing means having an input connected to the output of the differential amplifier across an amplifier, said processing means successively comprising an analog--digital converter, a first random access memory and a digital processing circuit, wherein the means for producing a reference voltage comprise a second random access memory having an input and an output, the input being connected to the output of the first random access memory across a switching circuit and a digital--analog converter having an input connected to the output of the memory and an output connected to the second input of the differential ampli