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1.引言在化工与石油加工技术中,人们往往对测量与调节设备提出了高标准严要求的同时,也希望降低其所需的使用费用。目前正在使用的测量与调节设备不外乎三类:纯电的、纯气的或电气混合系统。电子方面虽有许多显见的优点如:小型化、故障出现率小等。但目前仍然无法排挤掉气动系统,其主要原因在于气动的传递功效高,同时能在危险爆炸区中工作。另一方面气动也有不足之处,在考虑到系统允许的传递时间下,其最大的传递距离只能达到150～350公尺左右。显然取两者之长处,将电子——气动适当地结合,这是明智的。电子系统除了能在较远距离内迅速而可靠地传送信号外
1. Introduction In chemical and petroleum processing technologies, people often place high standards and strict requirements on measurement and regulation equipment, and they also hope to reduce their required usage fees. There are no more than three types of measurement and conditioning equipment currently in use: purely electric, pure gas or electric hybrid systems. Although there are many obvious advantages in electronics such as: miniaturization, failure rate is small and so on. However, the pneumatic system can not be squeezed out at present. The main reason is that pneumatic transmission has high efficiency and can work in a dangerous explosion zone. Pneumatic on the other hand there are shortcomings, taking into account the system allows the delivery time, the maximum transmission distance can only reach 150 to 350 meters. Obviously taking both strengths, the appropriate combination of electronic - pneumatic, it is wise. In addition to the electronic system can transmit signals quickly and reliably over long distances