The Research Of Electromagnetic Compatibility Of Non Invasive Intracranial Pressure Detection And Analysis Instrument

Medical Device relates to the health and safety of the public, as a special and important commodity. As an important indicator of medical electrical equipment, electromagnetic compatibility is essential to secure the validity and reliability of equipment. In this paper, non invasive intracranial pressure detection and analysis instrument is valuable for providing useful process for the electromagnetic compatibility design of medical electrical equipment. Its electromagnetic compatibility is analyzed by qualitative methods(location of interference sources and coupling approaches, risk analysis of mechanical structure) and quantitative method(shielding effectiveness model analysis) chronologically. The validity and correctness of analysis is confirmed by verification tests after the rectification. And on this basis, electromagnetic properties of printed circuit board of signal acquisition and conditioning are simulated, and methods of circuit optimization design are proposed.This paper includes the following aspects:(1) The tests and corresponding standards of medical electrical equipment are introduced. Test methods for each test, test equipment arrangements and test limits are described in detail according to standards and practical experience;(2) Interference sources and coupling approaches of the research equipment are located by spectrum analyzer and near field probe. It demonstrated that mainboard, acquisition card, switching power supply and monitor are interference sources, patient cables, power cable and internal USB cables are coupling approaches. The risk of mechanical structure design is analyzed after location, methods to reduce the risk of electromagnetic compatibility are proposed, and the equipment is rectificated technically by related components and materials purchased. Verification tests of full item of electromagnetic compatibility are carried out, all the tests pass in one attempt. It confirmed the validity of risk analysis and rectification;(3) Based on the classic Schelkunoff principle, the plane wave shielding model is deduced. The shielding model is modified because of enclosure pores. Therefore, shielding effectiveness calculation model is derived which can be applied in engineering practice;(4) Electromagnetic properties of printed circuit board of impedance signal acquisition and conditioning are simulated by CST PCB STUDIO. And methods of circuit optimization design are discussed. Representative traces and network are selected for the simulation of signal integrity and power integrity. The results of simulation confirm that wide line space or short coupling length, small media thickness and proper termination matching can minimize crosstalk noise between the transmission lines. Reasonable transmission line impedance matching, stable transmission signal can suppress the problem of signal reflection. And stable PDN system, decoupling of power/ground plane can reduce voltage noise.