Four Probe Method Parallel Connection Measure Of Current Tester Base On Operational Amplifier

With the intelligent society and the rapid development of science and technology,more and more new electronic products appear in the daily life and study.Products constituted of PCB in a routine inspection and maintenance work have become a strong guarantee of product inspection.The stand or fall of batch testing circuit board and circuit of current detection technology need to be further simplified,much faster and more accurate.Usually when doing current measurements,we need to connect the measuring instrument with the circuit,or penetrate the will be tested wire into the measuring magnetic ring.Therefore,doing a research concerning a new current-testing way of paralleling the wires will bring a lot of convenience and have a practical significance in many occasions such as PCB current measurement detection.Through the analysis of common several current measurement methods,this study aims at analyzing its advantages and disadvantages in-depth.Based on the current PCB online measure market phenomenon,we will design a low cost,small resistance wires which can parallel measurement method and circuit of electric current from a conductor.This circuit test base on the characteristics of operational amplifier and work style.We will choose a high gain,low disturbance type high precision amplifier as the core device,and parallel current measurement method was implemented.This method changes the inconvenience reduced by the traditional measurement of PCB in current detection method,making the measurement of the current line in small current situations such as PCB test overhaul implementation with no necessity to disconnect PCB copper foil become reality.The paper puts forward a kind of parallel current measurement circuit,including the main measurement circuit based on precision op-amp OP177 type,and a current range extension measuring circuit composed of the sampling resistor and IRF630 VMOS tube.This paper anal sizes and simulates the circuit principle in great details.In the meanwhile,analyzed and compared the selection of components by using PROTEUS simulation to verify the design of the circuit.Simulation results show that when the conductor resistancemeasured in 50 m ?,the current measurement error is 4% or less within the scope of 2 m A ~200 m A,and the current measurement error is less than 3% within the scope of the 3 m A ~200 m A.Practical circuit results show that when the conductor resistance measured in 50 m?,the current measurement error is 6% or less within the scope of 2 m A ~ 200 m A,and the current measurement error is less than 2% within the scope of the 4 m A ~ 200 m A.Tests show that the circuit can realize parallel current measurement,measurement error and the change trend tally with the simulation results.Mainly due to the simulation environment for ideal conditions and the actual measurement circuit of the experimental equipment,the environment and human reading,and many other factors.