电容式液位计/开关升级及与DCS接口改进

Upgrade of Capacitance Level Meter/Switch and Modification of Interface With DCS

原型号电容式液位计由探头和变送器组成,变送器为四线制4mA^20mA接口。新型号电容式液位计仅包括探头,探头为两线制4mA^20mA接口,即液开计升级导致与DCS的接口类型发生变化。新、原型号电容式液位开关均由探头和变送器组成,它们的变送器与DCS的接口相同,但由于安装方式问题,原型号液位开关变送器安装在DCS柜内而新型号液位开关变送器只能安装在就地的接线箱,即液开关升级导致DCS柜内与柜外的接口信号发生变化。为满足新型号液位计/开关的接口功能,并保证DCS柜内AI/DI模块的其他通道不受液位计/开关所在通道故障的影响,本文给出了电容式液位计/开关升级换型及其与DCS接口改进设计方案,并进行了相关影响分析。

The original level meter consists of probe and transmitter whose interface is four-wire 4~20mA.The upgraded level meter only consists of probe whose interface is two-wire 4~20mA,which means that the interface with DCS changes due to the upgrade of capacitance level meter.Both the upgraded level switch and the original one consist of probe and transmitter,and the transmitters of them have the same interface with DCS.However,due to the problem of installation mode,the transmitter of the original level switch is installed in DCS cabinet,while the transmitter of the upgraded level switch has to be installed in the local junction box.That is to say,the upgrading of level switch results in the change of interface signal between inside and outside of DCS cabinet.In order to meet the interface function of the upgraded level meter/ switch and ensure that the other channels of AI/DI modules in DCS cabinet are not affected by the fault of the channel where the level meter/ switch is located,this paper presents the design of upgrade of capacitance level meter/ switch and the modification of interface with DCS and the relevant analysis.