ERROR TESTING DEVICE

PURPOSE:To obtain an error testing device where the output of the A/D conversion of an original analogue signal and the digital output from a device to be tested are subjected to the calculation based on Fourier calculation and the error between the analogue signal and the digital signal is measured with a high precision on a basis of the calculation result. CONSTITUTION:The analogue signal of an applying power source 8 is inputted to a device 10 to be tested and a comparison testing device 17 through a line 9, and a signal coded digitally by the sampling signal from a line 18 in the device 10 is taken into a memory in an operating device 15 through an interface circuit 13. A signal subjected to digital conversion at the timing of a sampling circuit 14 in an A/D converting circuit 12 of the device 17 is taken into the memory of the operating device 15 also. An input fs(t) inputted directly to the device 17 and an output fx(t) of the device 10 are subjected to the operation based on the Fourier expansion in the operating device 15 to obtain errors in respect to DC components, amplitudes of harmonic waves, and phase components, and results are displayed on an output device 16.