OVERLOAD PREVENTER FOR ELECTROHYDRAULIC MATERIAL TESTER

摘要

PURPOSE:To prevent overload with a improved operability by overlapping the output of a displacement controlling amplifier with the output of a load controlling amplifier after a differential signal between a load applied and a load detected and a differential signal between the displacement set and the displacement detected are input into the displacement control amplifier. CONSTITUTION:A value of a displacement setting source 9 is adjusted by turning the set value of a load setting source 5 to 0 with a selector switch 12 ON. As the set displacement value grows large, a piston gets into contact with a sample and an error signal ELR is output based on a load detection signal EL which is detected with a load detector 3 and amplified with anamplifier 6 and the set load. The output i1 of a photo coupler driving amplifier A5 increases in proportion to the square of the change thereof and with a sharp drop in resistance value of a resistor RX, the displacement gain GS of a displacement controlling amplifier 11 reduces sharply as well. Therefore, a greater load error signal ELR will causes the gain GS to reduce even if the load gain GL of a load controlling amplifier 7 is rather low thereby preventing overloading with an automatically balanced control.