仪器仪表须在一些比较恶劣的环境如高温、低温、高温高湿、化工腐蚀性气体等条件下工作,所以需要密封性的外壳。但是为了要看清仪器仪表指示的读数,又必须在标度尺指示读数部位安装透明玻璃。由于玻璃与各种外壳材料(如胶木,铁壳等)的膨胀系数不同,因此怎样使外壳与玻璃密合能在各种环境的恶劣条件下不致破坏而保持密封,就成为仪器仪 Instrumentation to be in some of the more harsh environments such as high temperature, low temperature, high temperature and humidity, chemical corrosive gases and other conditions, so the need for airtight shell. However, in order to see the readings instructed by the instrumentation, transparent glass must be installed on the scale readings. As glass and a variety of shell materials (such as bakelite, iron, etc.) of the expansion coefficient is different, so how to make the shell and glass in close contact with the harsh environment in all kinds of harsh conditions and maintain the seal to become instrument