SYSTEM FOR OSCILLOSCOPE SIGNAL INPUT

PURPOSE:To lessen the influence upon a circuit to be measured and to improve the measurement precision, by providing an offset voltage applying means on the signal path from the tip of a probe to the signal input part of an oscilloscope. CONSTITUTION:The signal applied to a signal contact terminal 3 of a probe 1 is inputted to an adapter part 8 through a probe input resistance 5 and a signal cable 7 and is inputted to an input resistance 6 of an oscilloscope 2 through a mercury cell 9 of, for example, 1.3V. The output level of an ECL logical circuit to be measured is fluctuated in a range -0.8--1.8V, and the threshold level is -1.3V. When the output level of the circuit to be measured is -0.8V, 1mA is flowed to the oscilloscope side; and when the output level is -1.8V, 1mA is flowed to the circuit side reversely; and when the output level is the threshold level, no current is flowed in and out. Thus, the current flowed in and out between the circuit to be measured and the oscilloscope is reduced to lessen the influence upon the circuit to be measured.