A radon in soil gas measuring system based on Controller Area Network (CAN) bus is developed and introduced in this paper. Probes of the system can be buried in soil for radon long term measuring continuously. Undisturbed passive diffusing methods was used to collect radon in soil gas. A semi-conductor detector, Au surface-barrier type, was adopted for alpha particle detecting. Mean while, some parameter, such as gas temperature, pressure, and relative humidity, etc, was measured as well. An area radon detecting network can be set up for multi-point measurement at the same time, due to the technique of CAN bus. When configured with a portable control machine, probes can be running in a self-operate mode. Thus, no microcomputer is required. The self-operate mode means starting detecting according to the configured schedule, and the result, such as counting rate of alpha particle, gas temperature, pressure, and relative humidity, etc, will be saved automatically. These data can be conveniently display on the screen of the portable control machine, or copied to a microcomputer via the CAN bus.The protocol system was test. The counting rate of background is less than 2 counts per hour. The detecting resolution for gas temperature, pressure, and relative humidity is corresponding 0.1℃, 10Pa, and1%. The system can be powered from either a 12Volts battery or an AC adaptor. And the average power consumption for each probe is about 0.8Watts.Measuring work was done for days in air at room, in order to elementary study on the relationship between the counting rate of alpha particle and the meteorological condition. Results show that there was a significant positive correlation between the counting rate of alpha particle and air temperature. A significant passive dependence of the radon concentration on the atmospheric pressure was also found. And no appreciable dependence on relative humidity was revealed. But the minimum value of the humidity appeared when the radon concentration reached the maximum value.The system can meet the requirement on region of volcano and earthquake event forecast, catastrophic geological event monitor, and environmental radiation level survey, etc. It has better cost efficiency and would have a broadly market.
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