公开(公告)号：EP0886782A1

公开(公告)日：1998-12-30

申请号：EP97916140

申请日：1997-03-17

申请人： SYMETRIX CORP

发明人： DEVILBISS ALAN

IPC分类号： G01R31/00 ,  G01R19/00

CPC分类号： G01R19/0023

摘要： A first terminal (791) of a device-under-measurement (DUM) is connected to a buffer amplifier (758) and to the inverting input (747) of an operational amplifier (754). A second terminal (792) of the DUM is connected to a buffer amplifier (756) having its output (796) connected to the non-inverting input (746) of the operational amplifier (754). The non-inverting input is also connected to the output (793) of a signal generator (760). The second terminal (792) is also connected to ground (767) through a programmable load circuit (762). A circuit (779) creates a feedback loop from the DUM and the load circuit (762) to the operational amplifier (754) to enable the amplifier to maintain a predetermined voltage across the DUM and to isolate the amplifier from current flow from the load circuit (762). An oscilloscope (766) is connected across the outputs (727, 796) of the buffer amplifiers (758, 757) and a computer (764) controls the signal generator (760) in response to a signal from the oscilloscope and also controls the load (762) via a load control circuit (765).