许多贵重精密的电子仪器如放大器、示波器、心电图仪等电子线路是一种弱电系统。它都采用高阻抗回路,很易受雷电和周围空间电磁场的干扰。为了防止外来干扰,保证仪表仪器的工作质量,以往一些电子仪器常采用金属机壳屏蔽达到保护作用。但许多金属机壳制造工艺复杂,成本较高。近年来,许多电子仪器都改用美观、经济、坚固、耐蚀的工程塑料机 Many expensive precision electronic devices such as amplifiers, oscilloscopes, electrocardiographs and other electronic circuits is a weak system. It uses high-impedance loop, it is susceptible to lightning and electromagnetic interference in the surrounding space. In order to prevent external interference, to ensure the quality of the instrument instrument work, in the past some electronic instruments often used metal enclosure shielding to achieve the protection. However, many metal chassis manufacturing process is complicated and costly. In recent years, many electronic devices are used to beautiful, economical, sturdy, corrosion-resistant engineering plastic machine