The Construction Of Multi-physics Simulation Model And Noise Study Of The Seismometer Based On Molecular Electronic Transducer Technology

Years of practice has proved that the seismic exploration is a fast and effectivemethod for exploration of underground structure and the searching for resources suchas petroleum and natural gas. With the growing demand of petroleum and natural gas,our requirement to the seismic exploration is more and more strict. In many respects,the mainstream of the electromechanical geophone has been unable to meet therequirements and the geophone becomes a bottleneck for seismic explorationtechnology. Over the years, many companies and research institutions both at homeand abroad are committing to the development of the new type of geophone and manyof them have launched many products, such as piezoelectric ceramic geophone, eddygeophone, laser geophone, MEMS geophone and so on. The working principles ofthose geophones are different from the electromechanical geophone, and in somerespect they have better performance. However, on the whole, these kinds ofgeophones have some fatal flaws which lead to unable achieving large-scalecommercial promotion. Therefore, related companies and research institutes has notstopped the pace of development of new seismic geophone.MET seismic geophone is a new developed type of geophone in recent years, thiskind of geophone is based on the molecular electronic sensing technology principle.There are no mechanical devices such as solid block and spring which are necessaryfor the electromechanical geophone inside the MET seismic geophone which is mainlycomposed of an external conditioning circuit and electrochemical reaction cavity. Acertain concentration of electrolyte contains KI andI2is filled with theelectrochemical reaction cavity and a porous sheet sensitive element is in the middle ofthe cavity. The sensitive element integrated in two pairs of (four layers) electrodes isconnected with the external conditioning circuit. When working, we give the fourelectrodes a certain voltage which causes the electrolyte ions reactions occurring in thefour electrodes. Under the action of vibration signal, the electrolyte generates relativemotion to the sensitive element, thus resulting in a pair of electrodes’ reaction ratebecomes faster and the other pair becomes more slowly or remains the same. Thiscauses one pair of electrodes’ output current becomes large and the other pair of electrodes’ becomes small. We can detect the vibration through the measurement oftwo electrodes’ output current difference.This paper aims at three main problems during the process of optimizing theperformance of MET seismic geophone. The design of MET seismic geophone shouldchange in order to make it more suitable for different applications. As for seismicexploration, MET seismic geophone should have lowest noise level and the sensitivityrequirement can be slightly lower. When used for security equipment, the sensitivityrequirement should be higher and noise level can be slightly lower. Through study themulti-physics simulation model we can know how to change the internal designparameters to make the geophone in accordance with the above requirements. So, themulti-physics simulation model is the first issue studied in this paper. Second, theself-noise of MET seismic geophone must be considered in any situations. Only theself-noise below the detected vibration signals can we distinguish the signal from thenoise. Third, MET seismic geophone is significantly affected by temperature, so therelationship between the gain and the temperature is a problem that must be studied.According to the above problems, this paper carried out the following researchconcretely:(1) Building the multi-physics simulation model of MET seismic geophoneincluding fluid field, electric field, and ion diffusion migration process. Through thismodel we can observe the distribution of various physical parameters (such as currentdensity, ion flux, potential distribution, etc.) of sensitive element in micro structure inorder to deeply understand the working process of MET seismic geophone.(2) Building the self-noise measurement system for MET seismic geophone tomeasure the self-noise power spectrum.(3) Studying the effect of temperature on MET seismic geophone. We built twogain-test-systems according to the high temperature and the low temperature and gotthe gain-temperature curve.