The Development Of The Magnetic Resonance Signal Launched System With SPWM

The rational of underground engineering construction is increased gradually, along with the foundation engineering construction in our country. MRS(Magnetic resonance signal) as the only way can explored the underground water has been recognized by human being, As so far,it’s also used in underground engineering to exploring and prevent the disaster water in the tunnel and mine, which play an important role. Therefore the existing MRS instrument also has inconvenience in underground engineering which should be solved. Such as, the exploring measurement is too complexed and inconvenient to transport in narrow tunnel.The launched system in JLMRS-III is based on the method of LC resonance in H-bridge, the main feature is transformed the high voltage square into the high voltage sine wave by H-bridge. And the alternating current excitation magnetic field in the underground, which can caused hydrogen protons level transition phenomenon in the groundwater. But the frequency of sine current changed with the local Larmor frequency, so in order to achieving the maximum excitation effect, it’s necessary to changing the parameters of LC in resonance current. In the actual measurement, the parameters of inductance is consistent, using the same transmitter coil, so the only way is to changing the capacitance parameters, that’s the reason for using capacitance box.This paper focused on the special environment of tunnel and mine in the underground engineering, changing the basic launched principles, improved the JLMRS-III launched system. Designed overall scheme of the MRS launched system based on SPWM technology. Mainly depend on development of the H-bridge.The unique of this method is the method of product the high-voltage sine wave not using LC resonance, but with SPWM. Why using this method now but not previously, because this method is designed for exploring the disaster water in the tunnel which has special exploration environment. The required depth of this environment is nearer than the traditional way, so the requirement of amplitude of explored current is lower which using SPWM can reached to. The advantages of this method is removed the capacitance box in the launch system. Improving the portability of the instrument.In this paper, compared two kinds of method with simulation in Simulink, MATLAB, through the analyzed decided using “directly way ”, demonstrates the feasibility of the theory by simulation and principles, presents the sampling points as the interval is 200 Hz between 1k Hz and 3k Hz, and the coil capacitance correspond the sampling points. Which lay the foundation for subsequent designed hardware circuit.Take the examination of H-bridge and the launching system in the laboratory. Compared the parameters of JLMRS-III, the examination result is consistent, accordance to the requirements of the field experiment conditions.