Development Of Auxiliary Facility For Automatic Calibration Of Digital-ammeter Error

The current methods of automatic calibration need to communicate between equipments,however,many equipments are unable to meet the requirements in the realistic environment.As calibration forbid disassemble the related equipment,add data-communication function is not easy.Adopt the auxiliary facility,the data acquisition could be integrated from outside.In calibration of ammeter,the related equipment are standard current source and ammeter needed to calibrate.Because can't know the ammeter status in advance,the current source will overloading when it has open circuit problem in measurement circuit.To avoid the risk,and also the broken of automatic calibration which caused by standard current resource overloading,This article analyse the form and structure of the ammeter and current source,to research the mechanism of overloading accident.With the feedback data which gathered by the auxiliary facility,do judgment at the status of ammeter.In addition,with the periphery wires,relay controller are added to the auxiliary facility for selection the current circuit.When the ammeter has the open circuit problem,to avoid overloading,the current source always could connect to the closed circuit;when it is normal,stepper motor would drag the knob of standard current source to control the output current,and calibrating the ammeter then.The auxiliary facility get data by computer vision,the MCU(Microcontroller Unit)drag of stepper motor to rotate,and control the relay to select the circuit.The PC computer is master computer,as the calculate platform of computer vision,also be the carrier of logistic calibration business.MCU as the slave computer,it receives the control instruction which calculated by the PC computer,then control the output of standard source.This article mainly set forth designing and implement for MCU control circuit and figure recognition algorithm in the system,Then functional test carried out.The test proof that:during the ammeter status detection,the ammeter which has open circuit problem,can't cause the standard current source overloading,the indicated value could be obtained from the source and ammeter,and with the same tendency.During the formal calibration process,the obtained value is similar as which in manual calibrating.It means that,with the auxiliary facility,the status of calibrated ammeter can be get,and could automatic calibrate the indicate value error of numerical ammeter effectively.