Development Of Dynamic Bipolar Pulse Conductivity Meter

In recent years, the water issue of our country becomes a hotspot and affects variety of business and industries, especially to the agriculture. In such a country with huge population, the shortage and pollution of water resource has a fatal impact to the agriculture and hence may gradually harms the daily life of ours and our descendent. The current situation of water resource indicates more attention should be paid to its relevant research, how to ease this issue it is most urgent task need to be resolved. Conductivity is the key parameter in monitoring and analyzing water quality. Its relevant analytical instruments are well applied in fields of agriculture, industry and production business, etc.With the application field carry on expanding, especially in water quality monitoring and analyzing, instrument for measuring conductivity becomes one of the essentials. Usually electrode conductivity measurement method in the measurement process can be affected by various factors, the main factors are the electrode polarization effects, capacitance and temperature effects. Therefore how to improve the accuracy of the conductivity meter is the research problem needs to be overcome.Based on a profound literature review of international and domestic materials, and combining water resources projects run by Hydrogeology and Environmental Geology Survey Center of China Geological Survey Bureau, this paper proposed dynamic bipolar pulse measurement method as the measuring principle of the instrument and designed handheld conductivity meter. In this method, the excitation pulse signal is two alternating, opposite polarity square wave signal with the same amplitude. In this case, the measurement process not only weakens the electrode polarization effect, but also reduces the impact of capacitive effect on the measurement results.Instrument designed is mostly used in field work and is a battery-powered handheld device. Hence, in the premise of ensuring high-precision, the power consumption has to be as small as possible. The hardware design of the instrument takes the MSP430F5438 microcontroller as the core, and designs the low power supply module; In order to improve the effect of the capacitance effect, the dynamic bipolar pulse generator with the dynamic bipolar pulse method is designed; In order to reduce the influence of environmental temperature on the measurement results, the temperature compensation module circuit of RTC thermistor is designed; In order to guarantee the accuracy of the instrument in the full range, the automatic switching circuit of the range and the man-machine interaction module are designed. In software design, In order to eliminate the accidental pulse interference, the median filtering method is used to deal with the data collected, which can effectively eliminate the interference. According to the function of each module using the method of modular programming, the program chart of each function module is given, and the program of the instrument is programmed by C language. Experiments show that the instrument has a good performance and accuracy, the measurement range is 1 ~ 104μS / cm, the measurement error is ±1%, reached the instrument design needs.