Design And Implementation Of The Slave Machine Of The Three-Station Key Contact Resistance Tester

As a interface of human-computer interaction,the key applied to all aspects of production and life.For the mass production of key products,its electrical characteristics test is a kind of repetitive and mechanical work,the traditional manual method is not only inefficient,but also the detecting errors from fatigue of the body itself is inevitable,The test instrument of key contact resistance can solve these problems.There are many types of key tester on the market currently,but the most part focused on load test only.Compared to similar products abroad,technology is not mature,the measurement accuracy and stability are not enough.This thesis designed a data acquisition system for measuring of contact resistance.It designed 3-channel input of contact buttons on hardware,Using the ratio method of resistances measurement,The voltage signal of the two ends of the key resistance and the standard resistance to be measured was sent to the ADC conversion module by conditioning circuit processing.STM32 MCU read the data of AD conversion to the PC resolution in a certain kind of communications protocol through the USB interface.In software,because of USB is a equipment that required the host initiating the communication,so developing a USB application software based on MFC of VC++6.0 platform at PC,it is used to control the data conversion and data transmission and reception of the slave.Which Serial to USB interface used the serial Assistant for the command transmission and data reception.Test results showed that test data were not lost in the process of AD data acquisition and USB transmission.In terms of the effects the measurement,By measuring a variety of resistances found that resistances error smaller when measured resistances closer to the standard resistance,the measurement error of fixed resistance is less than 3%,it meets the design requirements.Based on excellent measuring accuracy of fixed resistances,the contact resistances of key showed a trend of high-low-flat-low-high change,which meet the changing trends of press in the pressing process of key.