PLC模拟量常见几种干扰与解决办法

<p style="margin-top: 0px; margin-bottom: 0px; padding: 0px; outline: 0px; max-width: 100%; clear: both; min-height: 1em; color: rgba(0, 0, 0, 0.9); font-size: 17px; letter-spacing: 0.544px; text-align: justify; text-wrap: wrap; font-family: -apple-system, BlinkMacSystemFont, &quot;Helvetica Neue&quot;, &quot;PingFang SC&quot;, &quot;Hiragino Sans GB&quot;, &quot;Microsoft YaHei UI&quot;, &quot;Microsoft YaHei&quot;, Arial, sans-serif; background-color: rgb(255, 255, 255); box-sizing: border-box !important; overflow-wrap: break-word !important;"><span style="margin: 0px; padding: 0px; outline: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; color: rgb(0, 0, 0); font-size: 14px;">电压电流的变化通过导线传输时有二种形态，我们将此称做“共模”和“差模”。设备的电源线、电话等的通信线、与其它设备或外围设备相互交换的通讯线路，至少有两根导线，这两根导线作为往返线路输送电力或信号。但在这两根导线之外通常还有第三导体，这就是“地线”。干扰电压和电流分为两种：一种是两根导线分别做为往返线路传输；另一种是两根导线做去路，地线做返回路传输。前者叫“差模”，后者叫“共模”。   </span><span style="margin: 0px; padding: 0px; outline: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-size: 14px;">     </span><br/></p><p style="margin-top: 0px; margin-bottom: 0px; padding: 0px; outline: 0px; max-width: 100%; clear: both; min-height: 1em; color: rgba(0, 0, 0, 0.9); font-size: 17px; letter-spacing: 0.544px; text-align: justify; text-indent: 0em; text-wrap: wrap; font-family: -apple-system-font, BlinkMacSystemFont, Arial, sans-serif; widows: 1; line-height: 1.75em; background-color: rgb(255, 255, 255); box-sizing: border-box !important; overflow-wrap: break-word !important;"><br/></p><p style="margin-top: 0px; margin-bottom: 0px; padding: 0px; outline: 0px; max-width: 100%; clear: both; min-height: 1em; color: rgba(0, 0, 0, 0.9); font-size: 17px; letter-spacing: 0.544px; text-align: justify; text-indent: 0em; text-wrap: wrap; font-family: -apple-system-font, BlinkMacSystemFont, Arial, sans-serif; widows: 1; line-height: 1.75em; background-color: rgb(255, 255, 255); box-sizing: border-box !important; overflow-wrap: break-word !important;"><span style="margin: 0px; padding: 0px; outline: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-size: 14px;">现场使用的显示仪表由于环境条件复杂，加之被测参数大多被转换成微弱的低电平电压信号，并经长距离传送到显示仪表，因此除有用的信号外，还会有一些与被测信号无关的干扰信号夹杂其中，它将影响测量结果的正确性，严重时会使仪表无法正常工作。现对产生干扰的途径及消除干扰的措施作一介绍。</span></p><p><section><section><span style="margin: 0px; padding: 0px; outline: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; color: rgb(63, 63, 63); font-size: 14px;"><strong style="margin: 0px; padding: 0px; outline: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important;">干扰途径</strong><strong style="margin: 0px; padding: 0px; outline: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important;"></strong></span></section><section><br/></section></section><section><p style="margin-top: 0px; margin-bottom: 0px; padding: 0px; outline: 0px; max-width: 100%; clear: both; min-height: 1em; line-height: 1.75em; text-indent: 0em; box-sizing: border-box !important; overflow-wrap: break-word !important;"><span style="margin: 0px; padding: 0px; outline: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; color: rgb(63, 63, 63); font-family: -apple-system-font, BlinkMacSystemFont, Arial, sans-serif; letter-spacing: 0.544px; font-size: 14px;">干扰源在仪表内、外部都有可能存在。如在仪表外部，大功率用电设备、大功率变压器、电力网都可能成为干扰源。而在仪表内部，电源变压器、线圈、继电器、开关以及电源线等都可能成为干扰源。干扰源常通过以下途径进入仪表。</span></p></section></p><p style="margin-top: 0px; margin-bottom: 0px; padding: 0px; outline: 0px; max-width: 100%; clear: both; min-height: 1em; color: rgba(0, 0, 0, 0.9); font-size: 17px; letter-spacing: 0.544px; text-align: justify; text-indent: 0em; text-wrap: wrap; widows: 1; font-family: -apple-system-font, BlinkMacSystemFont, Arial, sans-serif; line-height: 1.75em; background-color: rgb(255, 255, 255); box-sizing: border-box !important; overflow-wrap: break-word !important;"><br/></p><p style="margin-top: 0px; margin-bottom: 0px; padding: 0px; outline: 0px; max-width: 100%; clear: both; min-height: 1em; color: rgba(0, 0, 0, 0.9); font-size: 17px; letter-spacing: 0.544px; text-align: justify; text-indent: 0em; text-wrap: wrap; widows: 1; font-family: -apple-system-font, BlinkMacSystemFont, Arial, sans-serif; line-height: 1.75em; background-color: rgb(255, 255, 255); box-sizing: border-box !important; overflow-wrap: break-word !important;"><span style="margin: 0px; padding: 0px; outline: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; color: rgb(63, 63, 63); font-size: 14px;"><strong style="margin: 0px; padding: 0px; outline: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important;">1、信号源与仪表之间的连接导线、仪表内部的配线通过磁耦合在电路中形成干扰。</strong>在大功率变压器、交流电机、电力线和周围空间都存在有很强的交流磁场，而闭合回路处在这种变化的磁场中将感应出电势。这种感应电势与有用信号相串联，当传感器与显示仪表距离较远时，这种串模干扰尤为突出。</span></p><p style="margin-top: 0px; margin-bottom: 0px; padding: 0px; outline: 0px; max-width: 100%; clear: both; min-height: 1em; color: rgba(0, 0, 0, 0.9); font-size: 17px; letter-spacing: 0.544px; text-align: justify; text-indent: 0em; text-wrap: wrap; widows: 1; font-family: -apple-system-font, BlinkMacSystemFont, Arial, sans-serif; line-height: 1.75em; background-color: rgb(255, 255, 255); box-sizing: border-box !important; overflow-wrap: break-word !important;"><br/></p><p style="margin-top: 0px; margin-bottom: 0px; padding: 0px; outline: 0px; max-width: 100%; clear: both; min-height: 1em; color: rgba(0, 0, 0, 0.9); font-size: 17px; letter-spacing: 0.544px; text-align: justify; text-indent: 0em; text-wrap: wrap; widows: 1; font-family: -apple-system-font, BlinkMacSystemFont, Arial, sans-serif; line-height: 1.75em; background-color: rgb(255, 255, 255); box-sizing: border-box !important; overflow-wrap: break-word !important;"><span style="margin: 0px; padding: 0px; outline: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; color: rgb(63, 63, 63); font-size: 14px;"><strong style="margin: 0px; padding: 0px; outline: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important;">2、干扰源通过电容的耦合在回路中形成干扰，它是两电场相互作用的结果。</strong>通过静电耦合的方式，能在两输入端感应出对地的共同电压，以共模干扰的形式出现，由于共模干扰不和信号相叠加，它不直接对仪表产生影响。但它能通过测量系统形成到地的泄漏电流，该泄漏电流通过电阻的耦合就能直接作用于仪表而产生干扰。电磁感应、静电感应所形成的干扰大多是工频干扰电压，但变频器、带整流子的电机等会产生谐波干扰。由于雷电的作用在电力线上也会感应出干扰电压。</span></p><p style="margin-top: 0px; margin-bottom: 0px; padding: 0px; outline: 0px; max-width: 100%; clear: both; min-height: 1em; color: rgba(0, 0, 0, 0.9); font-size: 17px; letter-spacing: 0.544px; text-align: justify; text-indent: 0em; text-wrap: wrap; widows: 1; font-family: -apple-system-font, BlinkMacSystemFont, Arial, sans-serif; line-height: 1.75em; background-color: rgb(255, 255, 255); box-sizing: border-box !important; overflow-wrap: break-word !important;"><br/></p><p style="margin-top: 0px; margin-bottom: 0px; padding: 0px; outline: 0px; max-width: 100%; clear: both; min-height: 1em; color: rgba(0, 0, 0, 0.9); font-size: 17px; letter-spacing: 0.544px; text-align: justify; text-indent: 0em; text-wrap: wrap; widows: 1; font-family: -apple-system-font, BlinkMacSystemFont, Arial, sans-serif; line-height: 1.75em; background-color: rgb(255, 255, 255); box-sizing: border-box !important; overflow-wrap: break-word !important;"><span style="margin: 0px; padding: 0px; outline: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; color: rgb(63, 63, 63); font-size: 14px;"><strong style="margin: 0px; padding: 0px; outline: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important;">3、在一些测温场合，当将热电偶电极直接焊于通电加热的金属件上，由于金属件在平行于电流方向的各点存在电位差，这时引入的干扰电压也是很大的。</strong>在高温状态下，耐火材料的绝缘电阻急剧下降，热电偶的瓷保护管、瓷珠的绝缘性能也会下降，则电炉电源电压通过耐火砖、热电偶套管、瓷珠等泄漏到热电偶丝上，在热电偶电极与地之间产生干扰电压。</span></p><p style="margin-top: 0px; margin-bottom: 0px; padding: 0px; outline: 0px; max-width: 100%; clear: both; min-height: 1em; color: rgba(0, 0, 0, 0.9); font-size: 17px; letter-spacing: 0.544px; text-align: justify; text-indent: 0em; text-wrap: wrap; widows: 1; font-family: -apple-system-font, BlinkMacSystemFont, Arial, sans-serif; line-height: 1.75em; background-color: rgb(255, 255, 255); box-sizing: border-box !important; overflow-wrap: break-word !important;"><br/></p><p style="margin-top: 0px; margin-bottom: 0px; padding: 0px; outline: 0px; max-width: 100%; clear: both; min-height: 1em; color: rgba(0, 0, 0, 0.9); font-size: 17px; letter-spacing: 0.544px; text-align: justify; text-indent: 0em; text-wrap: wrap; widows: 1; font-family: -apple-system-font, BlinkMacSystemFont, Arial, sans-serif; line-height: 1.75em; background-color: rgb(255, 255, 255); box-sizing: border-box !important; overflow-wrap: break-word !important;"><span style="margin: 0px; padding: 0px; outline: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; color: rgb(63, 63, 63); font-size: 14px;"><strong style="margin: 0px; padding: 0px; outline: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important;">4、大地中各个不同点之间往往存在电位差，尤其在大功率用电设备附近，当这些设备的绝缘性能下降时，电位差更大。</strong>而现场仪表在使用中，有时不注意会使回路存在两个以上的接地点，就会把不同接地点的电位差引入到显示仪表中而形成共模干扰。</span></p><p style="margin-top: 0px; margin-bottom: 0px; padding: 0px; outline: 0px; max-width: 100%; clear: both; min-height: 1em; color: rgba(0, 0, 0, 0.9); font-size: 17px; letter-spacing: 0.544px; text-align: justify; text-indent: 0em; text-wrap: wrap; widows: 1; font-family: -apple-system-font, BlinkMacSystemFont, Arial, sans-serif; line-height: 1.75em; background-color: rgb(255, 255, 255); box-sizing: border-box !important; overflow-wrap: break-word !important;"><br/></p><p style="margin-top: 0px; margin-bottom: 0px; padding: 0px; outline: 0px; max-width: 100%; clear: both; min-height: 1em; color: rgba(0, 0, 0, 0.9); font-size: 17px; letter-spacing: 0.544px; text-align: justify; text-indent: 0em; text-wrap: wrap; widows: 1; font-family: -apple-system-font, BlinkMacSystemFont, Arial, sans-serif; line-height: 1.75em; background-color: rgb(255, 255, 255); box-sizing: border-box !important; overflow-wrap: break-word !important;"><span style="margin: 0px; padding: 0px; outline: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; color: rgb(63, 63, 63); font-size: 14px;"><strong style="margin: 0px; padding: 0px; outline: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important;">5、当仪表的桥路电源接地时，除桥路输出不平衡信号电压以外，信号线对地还有一公共电压，该公共电压不是所要测量的信号电压，而是共模干扰的一种表现。</strong></span></p><p><section><p style="margin-top: 0px; margin-bottom: 0px; padding: 10px 0px; outline: 0px; max-width: 100%; box-sizing: border-box; clear: both; min-height: 1em; text-indent: 0em; overflow-wrap: break-word !important;"><br/></p><section><section><section><section><span style="margin: 0px; padding: 0px; outline: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-size: 14px;">串模干扰</span></section></section><section><section><span style="margin: 0px; padding: 0px; outline: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-size: 14px;">共模干扰</span></section></section></section></section><p style="margin-top: 0px; margin-bottom: 0px; padding: 0px; outline: 0px; max-width: 100%; clear: both; min-height: 1em; box-sizing: border-box !important; overflow-wrap: break-word !important;"><br/></p></section><section><p style="margin-top: 0px; margin-bottom: 0px; padding: 0px; outline: 0px; max-width: 100%; clear: both; min-height: 1em; line-height: 1.75em; text-indent: 0em; box-sizing: border-box !important; overflow-wrap: break-word !important;"><span style="margin: 0px; padding: 0px; outline: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; color: rgb(63, 63, 63); letter-spacing: 0.544px; font-size: 14px;">串模干扰（差模干扰）与共模干扰（接地干扰）。以主板上的两条PCB走线（连接主板各元件的导线）为例，所谓串模干扰，指的是两条走线之间的干扰；而共模干扰则是两条走线和PCB地线之间的电位差引起的干扰。</span></p><p style="margin-top: 0px; margin-bottom: 0px; padding: 0px; outline: 0px; max-width: 100%; clear: both; min-height: 1em; line-height: 1.75em; text-indent: 0em; box-sizing: border-box !important; overflow-wrap: break-word !important;"><br/></p><p style="margin-top: 0px; margin-bottom: 0px; padding: 0px; outline: 0px; max-width: 100%; clear: both; min-height: 1em; line-height: 2em; text-indent: 0em; box-sizing: border-box !important; overflow-wrap: break-word !important;"><span style="margin: 0px; padding: 0px; outline: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; color: rgb(63, 63, 63); font-size: 14px;"><strong style="margin: 0px; padding: 0px; outline: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important;">1、串模干扰</strong></span></p><p style="margin-top: 0px; margin-bottom: 0px; padding: 0px; outline: 0px; max-width: 100%; clear: both; min-height: 1em; line-height: 1.75em; text-indent: 0em; box-sizing: border-box !important; overflow-wrap: break-word !important;"><span style="margin: 0px; padding: 0px; outline: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; color: rgb(63, 63, 63); font-size: 14px;">串模干扰（差模干扰）与共模干扰（接地干扰）。以主板上的两条PCB走线（连接主板各元件的导线）为例，所谓串模干扰，指的是两条走线之间的干扰；而共模干扰则是两条走线和PCB地线之间的电位差引起的干扰。</span></p><p style="margin-top: 0px; margin-bottom: 0px; padding: 0px; outline: 0px; max-width: 100%; clear: both; min-height: 1em; line-height: 1.75em; text-indent: 0em; box-sizing: border-box !important; overflow-wrap: break-word !important;"><br/></p><p style="margin-top: 0px; margin-bottom: 0px; padding: 0px; outline: 0px; max-width: 100%; clear: both; min-height: 1em; text-indent: 0em; box-sizing: border-box !important; overflow-wrap: break-word !important;"><img class="rich_pages wxw-img" width="677px" src="https://mmbiz.qpic.cn/mmbiz_png/IbK8vRh9Eqm5ohGOEWpUYpicO8uwgqNDuqXW5BB2eAvlWJF8F6mbQWXFfXQIvvCq3M3TwztjhkWQ6zDdlaNFB1w/640?wx_fmt=png&tp=wxpic&wxfrom=5&wx_lazy=1&wx_co=1" alt="图片" style="margin: 0px; padding: 0px; outline: 0px; vertical-align: bottom; box-sizing: border-box !important; overflow-wrap: break-word !important; height: auto !important; visibility: visible !important; width: 677px !important;"/></p><p style="margin-top: 0px; margin-bottom: 0px; padding: 0px; outline: 0px; max-width: 100%; clear: both; min-height: 1em; line-height: 1.75em; text-indent: 0em; box-sizing: border-box !important; overflow-wrap: break-word !important;"><br/></p><p style="margin-top: 0px; margin-bottom: 0px; padding: 0px; outline: 0px; max-width: 100%; clear: both; min-height: 1em; line-height: 1.75em; text-indent: 0em; box-sizing: border-box !important; overflow-wrap: break-word !important;"><span style="margin: 0px; padding: 0px; outline: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; color: rgb(63, 63, 63); font-size: 14px;">测量串模干扰电压，以往推荐用电子管电压表，在现场可使用有交流毫伏挡的数字万用表进行测量。如上图所示，把电压表跨接在仪表输人的正、负端之间测量，通常串模干扰电压大多在几毫伏到几十毫伏范围内。</span></p><p style="margin-top: 0px; margin-bottom: 0px; padding: 0px; outline: 0px; max-width: 100%; clear: both; min-height: 1em; line-height: 1.75em; text-indent: 0em; box-sizing: border-box !important; overflow-wrap: break-word !important;"><br/></p><p style="margin-top: 0px; margin-bottom: 0px; padding: 0px; outline: 0px; max-width: 100%; clear: both; min-height: 1em; line-height: 2em; text-indent: 0em; box-sizing: border-box !important; overflow-wrap: break-word !important;"><span style="margin: 0px; padding: 0px; outline: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; color: rgb(63, 63, 63); font-size: 14px;"><strong style="margin: 0px; padding: 0px; outline: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important;">2、共模干扰</strong></span></p><p style="margin-top: 0px; margin-bottom: 0px; padding: 0px; outline: 0px; max-width: 100%; clear: both; min-height: 1em; line-height: 1.75em; text-indent: 0em; box-sizing: border-box !important; overflow-wrap: break-word !important;"><span style="margin: 0px; padding: 0px; outline: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; color: rgb(63, 63, 63); font-size: 14px;">共模干扰是指干扰电压出现在仪表任一输入端（正端或负端）对地之间的交流信号，这种干扰又称为“对地干扰”和“纵向干扰”。</span></p><p style="margin-top: 0px; margin-bottom: 0px; padding: 0px; outline: 0px; max-width: 100%; clear: both; min-height: 1em; line-height: 1.75em; text-indent: 0em; box-sizing: border-box !important; overflow-wrap: break-word !important;"><br/></p><p style="margin-top: 0px; margin-bottom: 0px; padding: 0px; outline: 0px; max-width: 100%; clear: both; min-height: 1em; text-indent: 0em; box-sizing: border-box !important; overflow-wrap: break-word !important;"><img class="rich_pages wxw-img" width="677px" src="https://mmbiz.qpic.cn/mmbiz_png/IbK8vRh9Eqm5ohGOEWpUYpicO8uwgqNDuPeCuFcnibH4iadqXeYrI7y4vibPZp4ibtGuT0NxDFStoRm3d9J1PZT7aiaQ/640?wx_fmt=png&tp=wxpic&wxfrom=5&wx_lazy=1&wx_co=1" alt="图片" style="margin: 0px; padding: 0px; outline: 0px; vertical-align: bottom; box-sizing: border-box !important; overflow-wrap: break-word !important; height: auto !important; visibility: visible !important; width: 677px !important;"/></p><p style="margin-top: 0px; margin-bottom: 0px; padding: 0px; outline: 0px; max-width: 100%; clear: both; min-height: 1em; line-height: 1.75em; text-indent: 0em; box-sizing: border-box !important; overflow-wrap: break-word !important;"><br/></p><p style="margin-top: 0px; margin-bottom: 0px; padding: 0px; outline: 0px; max-width: 100%; clear: both; min-height: 1em; line-height: 1.75em; text-indent: 0em; box-sizing: border-box !important; overflow-wrap: break-word !important;"><span style="margin: 0px; padding: 0px; outline: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-size: 14px;"><span style="margin: 0px; padding: 0px; outline: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; color: rgb(63, 63, 63);">测</span><span style="margin: 0px; padding: 0px; outline: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; color: rgb(63, 63, 63); text-indent: 0em; letter-spacing: 0.544px;">量共模干扰电压，可以用高阻电压表测量，也可使用数字万用表的交流电压挡进行测量。如上图所示，先把电压表接在仪表输人的正端与地之间测量，然后再把电压表接在仪表输人的负端与地之间测量，通常共模干扰电压大多在几伏到几十伏范围之内。</span></span></p><p style="margin-top: 0px; margin-bottom: 0px; padding: 0px; outline: 0px; max-width: 100%; clear: both; min-height: 1em; line-height: 1.75em; text-indent: 0em; box-sizing: border-box !important; overflow-wrap: break-word !important;"><br/></p><section><section><section><section><section><span style="margin: 0px; padding: 0px; outline: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-size: 14px;">抗干扰来源</span></section></section><section><section><span style="margin: 0px; padding: 0px; outline: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-size: 14px;">抗干扰措施</span></section></section></section></section></section><p style="margin-top: 0px; margin-bottom: 0px; padding: 0px; outline: 0px; max-width: 100%; clear: both; min-height: 1em; line-height: 1.75em; text-indent: 0em; box-sizing: border-box !important; overflow-wrap: break-word !important;"><br/></p><p style="margin-top: 0px; margin-bottom: 0px; padding: 0px; outline: 0px; max-width: 100%; clear: both; min-height: 1em; line-height: 1.75em; text-indent: 0em; box-sizing: border-box !important; overflow-wrap: break-word !important;"><span style="margin: 0px; padding: 0px; outline: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; color: rgb(63, 63, 63); font-size: 14px;">在现场要克服和消除串模干扰及共模干扰，首先要搞清楚干扰的来源，才有可能采取措施来克服干扰。</span></p><p style="margin-top: 0px; margin-bottom: 0px; padding: 0px; outline: 0px; max-width: 100%; clear: both; min-height: 1em; line-height: 1.75em; text-indent: 0em; box-sizing: border-box !important; overflow-wrap: break-word !important;"><br/></p><p style="margin-top: 0px; margin-bottom: 0px; padding: 0px; outline: 0px; max-width: 100%; clear: both; min-height: 1em; line-height: 1.75em; text-indent: 0em; box-sizing: border-box !important; overflow-wrap: break-word !important;"><span style="margin: 0px; padding: 0px; outline: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; color: rgb(63, 63, 63); font-size: 14px;"><strong style="margin: 0px; padding: 0px; outline: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important;">串模干扰的来源：大功率变压器、交流电动机、变频器等都有较强的交变磁场，如果仪表测量及控制的连接导线通过交变磁场，就会受到这些交变磁场的作用，在仪表的输入回路中感应出交流电压，而成为干扰信号。</strong></span></p><p style="margin-top: 0px; margin-bottom: 0px; padding: 0px; outline: 0px; max-width: 100%; clear: both; min-height: 1em; line-height: 1.75em; text-indent: 0em; box-sizing: border-box !important; overflow-wrap: break-word !important;"><br/></p><p style="margin-top: 0px; margin-bottom: 0px; padding: 0px; outline: 0px; max-width: 100%; clear: both; min-height: 1em; line-height: 1.75em; text-indent: 0em; box-sizing: border-box !important; overflow-wrap: break-word !important;"><span style="margin: 0px; padding: 0px; outline: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; color: rgb(63, 63, 63); font-size: 14px;">在现场为了克服串模干扰对仪表、控制系统的影响，可采取以下措施：</span></p><p style="margin-top: 0px; margin-bottom: 0px; padding: 0px; outline: 0px; max-width: 100%; clear: both; min-height: 1em; line-height: 1.75em; text-indent: 0em; box-sizing: border-box !important; overflow-wrap: break-word !important;"><span style="margin: 0px; padding: 0px; outline: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; color: rgb(63, 63, 63); font-size: 14px;">1、如热电偶、分析仪表的信号线要运离强电磁场，不要离动力线太近；</span></p><p style="margin-top: 0px; margin-bottom: 0px; padding: 0px; outline: 0px; max-width: 100%; clear: both; min-height: 1em; line-height: 1.75em; text-indent: 0em; box-sizing: border-box !important; overflow-wrap: break-word !important;"><span style="margin: 0px; padding: 0px; outline: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; color: rgb(63, 63, 63); font-size: 14px;">2、不要把仪表信号线、控制信号线与动力线平行放在同一个桥架托盘内，或穿在同一根穿线管内必要时信号线应使用屏蔽电线或屏蔽电缆，线的屏蔽层要采取一端接地的方式；</span></p><p style="margin-top: 0px; margin-bottom: 0px; padding: 0px; outline: 0px; max-width: 100%; clear: both; min-height: 1em; line-height: 1.75em; text-indent: 0em; box-sizing: border-box !important; overflow-wrap: break-word !important;"><span style="margin: 0px; padding: 0px; outline: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; color: rgb(63, 63, 63); font-size: 14px;">3、在仪表输入端加滤波电路；</span></p><p style="margin-top: 0px; margin-bottom: 0px; padding: 0px; outline: 0px; max-width: 100%; clear: both; min-height: 1em; line-height: 1.75em; text-indent: 0em; box-sizing: border-box !important; overflow-wrap: break-word !important;"><span style="margin: 0px; padding: 0px; outline: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; color: rgb(63, 63, 63); font-size: 14px;">4、对于智能仪表要根据现场情况设置数字滤波常数必要时再增加滤波电路的级数。</span></p><p style="margin-top: 0px; margin-bottom: 0px; padding: 0px; outline: 0px; max-width: 100%; clear: both; min-height: 1em; line-height: 1.75em; text-indent: 0em; box-sizing: border-box !important; overflow-wrap: break-word !important;"><br/></p><p style="margin-top: 0px; margin-bottom: 0px; padding: 0px; outline: 0px; max-width: 100%; clear: both; min-height: 1em; line-height: 1.75em; text-indent: 0em; box-sizing: border-box !important; overflow-wrap: break-word !important;"><span style="margin: 0px; padding: 0px; outline: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; color: rgb(63, 63, 63); font-size: 14px;"><strong style="margin: 0px; padding: 0px; outline: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important;">共模干扰的来源：高压电场的干扰；测量电炉温度时引入的干扰，如在高温下，电加炉的电源通过耐火砖、热电偶的瓷保护套管泄漏到热电偶上，使热电偶与地之间产生干扰电压；由于地电位不同而引入的干扰；还有氨合成塔用电加热器升温时也会对热电偶造成干扰。其干扰源大多是交流电压也有可能是直流电压。</strong><strong style="margin: 0px; padding: 0px; outline: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important;"></strong></span></p><p style="margin-top: 0px; margin-bottom: 0px; padding: 0px; outline: 0px; max-width: 100%; clear: both; min-height: 1em; line-height: 1.75em; text-indent: 0em; box-sizing: border-box !important; overflow-wrap: break-word !important;"><br/></p><p style="margin-top: 0px; margin-bottom: 0px; padding: 0px; outline: 0px; max-width: 100%; clear: both; min-height: 1em; line-height: 1.75em; text-indent: 0em; box-sizing: border-box !important; overflow-wrap: break-word !important;"><span style="margin: 0px; padding: 0px; outline: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; color: rgb(63, 63, 63); letter-spacing: 0.544px; font-size: 14px;">在现场为了克服共模干扰对仪表、控制系统的影响，所以可采取以下措施：<br/></span></p><p style="margin-top: 0px; margin-bottom: 0px; padding: 0px; outline: 0px; max-width: 100%; clear: both; min-height: 1em; line-height: 1.75em; text-indent: 0em; box-sizing: border-box !important; overflow-wrap: break-word !important;"><span style="margin: 0px; padding: 0px; outline: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; color: rgb(63, 63, 63); font-size: 14px;">1、把测量热电偶浮空；<br/></span></p><p style="margin-top: 0px; margin-bottom: 0px; padding: 0px; outline: 0px; max-width: 100%; clear: both; min-height: 1em; line-height: 1.75em; text-indent: 0em; box-sizing: border-box !important; overflow-wrap: break-word !important;"><span style="margin: 0px; padding: 0px; outline: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; color: rgb(63, 63, 63); font-size: 14px;">2、仪表放大器也采取浮空；<br/></span></p><p style="margin-top: 0px; margin-bottom: 0px; padding: 0px; outline: 0px; max-width: 100%; clear: both; min-height: 1em; line-height: 1.75em; text-indent: 0em; box-sizing: border-box !important; overflow-wrap: break-word !important;"><span style="margin: 0px; padding: 0px; outline: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; color: rgb(63, 63, 63); font-size: 14px;">3、如果测量对象允许则不要用露端式热电偶以避免热电极接地；<br/></span></p><p style="margin-top: 0px; margin-bottom: 0px; padding: 0px; outline: 0px; max-width: 100%; clear: both; min-height: 1em; line-height: 1.75em; text-indent: 0em; box-sizing: border-box !important; overflow-wrap: break-word !important;"><span style="margin: 0px; padding: 0px; outline: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; color: rgb(63, 63, 63); font-size: 14px;">4、热电偶保护套管要可靠接地；</span></p><p style="margin-top: 0px; margin-bottom: 0px; padding: 0px; outline: 0px; max-width: 100%; clear: both; min-height: 1em; line-height: 1.75em; text-indent: 0em; box-sizing: border-box !important; overflow-wrap: break-word !important;"><span style="margin: 0px; padding: 0px; outline: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; color: rgb(63, 63, 63); font-size: 14px;">5、使用屏蔽线时采用等电位屏蔽方式；</span></p><p style="margin-top: 0px; margin-bottom: 0px; padding: 0px; outline: 0px; max-width: 100%; clear: both; min-height: 1em; line-height: 1.75em; text-indent: 0em; box-sizing: border-box !important; overflow-wrap: break-word !important;"><span style="margin: 0px; padding: 0px; outline: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; color: rgb(63, 63, 63); font-size: 14px;">6、在信号线上加装旁路电容器。</span></p></section></p><p><br/></p>