Research On The Integrated Testing System Of Current/Frequency Converting Circuit

In order to fast and accurately measure the performance parameters of inertial important component of the accelerometer unit current/frequency conversion circuit (I/F conversion circuit) in inertial navigation system,In this paper, a test system of I/F converter circuit is designed. The constant current signal, sinusoidal current signal and transient step signal of the system are provided by the program controlled constant current source and adopt a FPGA chip as the core.Accurate measurement of the frequency signal of the output of the frequency measurement circuit, The static, dynamic and transient responses of three kinds of I/F converter circuits are analyzed.Firstly,the paper introduces the technology and research status of Inertial Navigation Component component test, then discusses the main contents and system design, and compare the advantages and disadvantages of various design options, and finally conclude the program based on FPGA with Verilog language in Quartus II Software Development platform. FPGA programmable constant current source output current control signal and controls the frequency of the signal collection, the data via the serial port to upload the application of PC to dispiay and saved.I/F converter circuit test system consists of two parts-the hardware design and software design.The part of the hardware circuit uses Altera’s Cyclone II series FPGA chip models EP2C8Q208C8N as processor chip. The programmable constant current source circuit is componented by the D/A converter TLC5615 and the integrated operational amplifier OPA2604,which provides a current signal for the test systems. The signal isolation circuit adapts to optocoupler 4N25 and uses the 74LS04 inverter as isolation plastic, so that the measured circuit output pulse signals are changed into a standard TTL signals.The serial hardware circuit uses MAX3232 chip to complete the design of RS232 interface circuit. Software design uses Quartus II software as a development platform, and the hardware controlling logic programming language Verilog to design the constant current source output module,to achieve output quiescent current signal, sinusoidal current signal, and transient step current signal. The pulse measurement module is designed to measure pulse signal output sensing circuit accurately, the measured data will be uploaded to PC through the serial port to be displayed,saveded and printed.The PC-based application programming interface is designed to Visual C++6.0 development environment software MFC dialog, it can down-bit crew machine to send the start and end of test control commands, which is used to display and save measurement results inorder to realize I/F converter circuit characteristics test function.At last, the paper debugs the hardware and software of the test system, and analyzes the measurement results. The experimental consequence reveals that this system can not only effectively test the characteristics of the current/frequency converter circuit, dynamic, transient, but also keep a long-term and stable operation,Which can greatly shorten the development cycle, improve the stability and reliability of the test system, and has some practical value.