In the invention, different offset voltages are added to multiple detected signals to be displayed. The said signals switched in turn are input to oscilloscope and displayed at different positions on the oscilloscope. Since visual persistence of human eye and display character of long afterglow of oscilloscope, visual effect seems that multiple detected signals are displayed on the oscilloscope at same time, even if the said signals are displayed in turn. Thus, one oscilloscope and one switching instrument can replace function of several oscilloscopes (in present, 3 oscilloscopes). The invention possesses advantages of simplified use, lowering energy consumption and saving facility resources. |