Design And Implementation Of Portable Common Building Ground Resistance Measuring Instrument

Ground connection is the key to lightning protection and disaster reduction of building.The stand of ground connection leads to the success of lightning protection directly.The purpose of the grounding connection is to drain the large current which generated by thunder on the earth effectively and rapidly.The grounding resistance is one of mine equipment diffuser effect of key indicators.And the size of grounding resistance is one of the key indicators of scattered flow effect of lightning protection devices.So measuring grounding resistance accurately is not only the important methods of judging whether the grounding device meets the relevant requirements but also the most major technical reference of lightning protection and disaster mitigation.If measuring the grounding resistance fast,accurate and scientifically,reasonable testing method and detection equipment which is simple and quick should be used.Based on the analysis and comparison of earth resistance measurement principle,three levels of compensation method measuring scheme is used in this paper combining with the characteristics of urban network of general buildings.Based on the scheme,a set of building lightning proof grounding resistance test system is designed.The test system is based on a series of STM32 processor and collecting the data of voltage and current signals by multi-channel parallel synchronous AD converter chip AD7656 do some filtering process with FFT algorithm thus achieving precise grounding resistance value.In order to make inspection business standardization and further improve the work efficiency,develop test software realization for the controlling of the modules,data storage,drawing a diagram of the building and entry building-related information,and other functions on the Wince system.Firstly,starting from the grounded concept,and analysis the constitution of the building ground network and related concepts of grounding resistor gradually,then introduce the theory of grounding resistance measurement from the wiring method.Secondly,introduce the hardware design plan.Measuring instrument hardware are designed modularly which are mainly constituted by the communication synthesis module,voltage current acquisition module,power management and communication module,power supply circuit and Wince system.And analyze working process of the hardware structures one by one.Then introduce idea of the software design and process analysis of each module and do corresponding research on the noise filtering method in signal acquisition at the same time.Finally make an analysis of the experimental measurement and introduce the instrument calibration methods.Built-in rechargeable lithium battery power supply scheme is put forward,and a reasonable power management system is designed due to the portability of the instrument in order to monitor on the related operation parameters such as current of the power supply,battery and environmental temperature to ensure the working safety of instrument.