热电偶测量应用.docVIP

目录 前言·····································································································2 2 热电偶的结构、种类、测温原理与特点···············································2 2.1热电偶结构·····················································································2 2.2热电偶种类及用途··········································································2 2.3热电偶的测温原理··········································································4 2.4热电偶的冷端温度补偿···································································5 2.5热电偶在石油化工应用上的优点····················································5 3.热电偶温度测量系统的组成与故障分析···············································5 3.1热电偶温度测量系统组成·······························································5 3.2热电偶温度测量的故障分析方法····················································6 3.3热电偶温度测量系统典型故障························································6 3.4热电偶温度测量故障分析及处理的应用实例··································7 4结束语·····································································································7 热电偶温度测量的应用与故障分析 摘要: 本文主要介绍热电偶的结构、种类、测温原理与特点.通过分析热电偶在石油化工装置的实际应用,总结热电偶测温过程中测量温度异常的多种原因,并指出了解决思路和方法。 关键词:热电偶 测温原理 应用 故障分析 1 前言 在石油化工工业生产过程中,温度是需要测量和控制的重要参数之一,它与压力、流量、物位合称工业测量与控制的四大参数。温度测量与控制的准确与否，将直接影响工业生产装置能否如期投产并正常运行。热电偶作为目前应用极为广泛的温度传感器，在工业生产的温度测量与自动化控制中具有非常重要的作用。 2 热电偶的结构、种类、测温原理与特点 2.1热电偶结构 热电偶由热电偶电极、绝缘子、保护管和接线盒组成。热电偶由电极焊接而成，可以是对接焊，也可以预先把两根电极绞缠在一起焊,缠绕圈数不超过3圈，否则测温工作点不是在焊接点，而是在缠绕处的末端。为保证两热电极之间绝缘，在两热电极上分别套入绝缘子（瓷管、石英管），防止极与极之间、极与保护管之间短路。保护管用于保护热电极免受化学腐蚀和机械损伤。保护管一般为无缝钢管、不锈钢管等，工作端通常为封闭（少数也使用露头端），热电极插入保护管内，热电极冷端两极分别接于保护管上端接线盒的接线端子上。 附图： 2.2热电偶种类及用途 常用热电偶可分为标准热电偶和非标准热电偶两大类。所标准热电偶是指国家标准规定了其热电势与温度的关系、允许误差、并有统一的标准分度表的热电偶，它有与其配套的显示仪表可供选用。非标准化热电偶在使用范围或数量级上均不及标准化热电偶，一般也没有统一的分度表，主要用于某些特殊场合的测量。我国从1988年1月1日起热电偶标准化，热电偶和热电阻全部按IEC国际标准生产，并指定S、B、E、K、R、J、T七种标准化热电偶为我国统一设计型热电偶。S分度号的特点是抗氧化性能强，宜在氧化性、惰性气中连续使用，长期使用温度1400℃，短期1600℃。在所有热电偶中，S分度号的精确度等级最高，通常用作标准热电偶；??? R分度号与S分度号相比除热电动势大15%左右，其它性能几乎完全相同； B分度号在室温下热电动势极小，故在测量时一般不用补偿导线。它的