PURPOSE: To ensure data with a high accuracy having a better reproducibility of test conditions through an automatic control from the setting of the test conditions to its driving.

CONSTITUTION: A temperature controller 3 on-off controls a heater in a thermostatic bath tank to keep the temperature in an electlytic cell constant. With a start-up switch on, an deairing is performed in the solution for a fixed time with a deairing time controller 5. Then a potential applying device is actuated with a potential sweep device 7 will be retained for a time set by a retention time controller 8. As the set time elapses, the potential is swept in the opposite direction at the speed set by a reverse sweep speed controller 9. Upon the end of the test, an proper announcement is made by an alarm 10.