【正文】 ystem include setting value of pressure of the proportional relief valve , Stimulating signals of valve coil to be tested produced by signal generator . The amplify signals of the servo valve to be tested in the above signals are current signals and the others are voltage signal . As these signals detected by the sensor usually contain noise or through modulation . So the signals should go through corresponding treatment before being inputed into the puter , then converted into digital signals by A/D converter for further use . Separate digital signal generator is used during the test ,and the signal generator use single chip microputer 16 as its core and can produce triangle waves, sine waves, square waves, linear sweep sine wave signals with the frequency of 0～ 800HZ and so on for servo valve testing . Signal generator municate with the main puter by RS232 . During the test , the main 9 puter tell signal generator the parameters such as generative type of waveform , amplitude and frequency of waveform . Signal generator produce stipulated type of waveform and input it into the servo amplifier of the valve to be tested . During the test of dynamic characteristics , transport the produced waveform data into the mian puter at the same time for calculating dynamic characteristics . Circuit structure of the system is shown in Figure 2. current signal i ofvalve to be t es te dpressure signal 12,13, 14,15flow sign al 1 6leakage flow signal 5sinusoidal cu rr en tsignal of valve to betes tedvelocity tran sd uc er 2 0sig nalinputchammelandcon dit ion ingdatecollectcardtestingsys temdigital signal g en er at orservo amplifie r of v al ve to be testedsig nalout putchannelpressure s et ti ngdra w d yna miccharacteristics curvetest result do cu me ntand date conservation current signal of testing syste m 5. Software of testing system The main function of the software system is to plete the disposition of measured data and draw the testing curve . So the system can be divided into signal processing module , data munication module , interface management module 10 and auxiliary function modules responsible for test document processing and data storage . These modules also contain a number of submodule respectively , and then submodule call the function of basic library functions to plete their respective functions. Signal processing module is the most important module of the test system and its submodules include digital filtering, curve fitting , the difference, frequency response calculation and error pensation. Algorithms can be used by digital filtering conclude median filtering , correlation filtering , limited convergence filtering and so on . We can choose the appropriate filtering method according to field interfere circumstance . Leastsquares principle is usually used in curve fitting to make error sum squares of curve points the minimum . Frequency response calculation includes the calculation of autocorrelation and crosscorrelation calculation . The relevant calculation uses the fast Fourier transform and inverse transform to achieve fast correlation algorithm . Functions of munication module include read and write input/output data buffer, modules of municate with each other of digital signal generator. Before the test , operator put needed pressure , channel of flow signal and waveform parameters of signal generator into the system .The system will call the buffer zone to establish the function and municating functions to establish data buffering area of each channel and send parameters to the signal generator and start the D / A and A / D data conversion at the same time . Each channel using interrupt mode to write data into the buffer zone . CPU reads the data of each buffer zone at intervals 11 of 1s and call interface processing management module to refresh the output interface after date diaposition . Interface management module is mainly responsible for the drawing of static and dynamic characteristic process is pleted by esch submodule through calling Plot（） function . Auxiliary function modules includes test data formatted output to a file, and test documents and data printing . The entire test system was developed under Microso