按工况与需求梳理选型逻辑，给出可落地的判断顺序。Practical selection logic organised by duty and requirement.
在线水质仪表选型不是先挑型号，而是先明确「测什么指标、什么工况、怎么装、怎么维护」。本文按六个步骤给出一套可落地的选型框架。Selecting online water-quality instruments starts not from a model number but from four questions: what to measure, under what conditions, how to install, and how to maintain. This article gives a practical six-step framework.
阅读全文Read more 选型指南 / Selection guides荧光法与膜法溶解氧仪在原理、维护量与适用场景上差别明显。本文给出两者的对比与选型建议，以及标定与常见故障处理方法。Optical (fluorescence) and membrane (electrochemical) dissolved oxygen sensors differ clearly in principle, maintenance and suitable duties. This article compares them and covers calibration and troubleshooting.
阅读全文Read more 选型指南 / Selection guides脱水效果不理想，多数是絮凝剂型号或投加量没匹配好。本文讲清阳离子 PAM 的关键指标、烧杯实验方法、配制与投加要点，以及常见问题处理。Poor dewatering is usually a flocculant grade or dose mismatch, not a machine problem. This article covers the key parameters of cationic PAM, the jar test method, make-up and dosing points, and troubleshooting.
阅读全文Read more 选型指南 / Selection guides电磁流量计与超声波流量计各有明确的适用边界。本文从介质、精度、安装、成本四个维度做对比，并给出直管段、接地等安装要点。Electromagnetic and ultrasonic flow meters each have clear application boundaries. This article compares them across medium, accuracy, installation and cost, and gives installation points such as straight runs and earthing.
阅读全文Read more 选型指南 / Selection guides液位测量方式很多，选错往往不是精度不够，而是工况不匹配。本文按介质与工况给出超声波、雷达、静压式等测量方式的适用边界。There are many ways to measure level, and mistakes usually come from a mismatch with the duty rather than insufficient accuracy. This article sets out where ultrasonic, radar and hydrostatic methods fit.
阅读全文Read more 选型指南 / Selection guides户外、潮湿、粉尘与爆炸性环境对仪表的外壳防护与防爆型式有明确要求。本文讲清 IP 等级与常见防爆标志的含义，以及选型时的核对顺序。Outdoor, damp, dusty and hazardous-area duties impose clear requirements on enclosure protection and explosion protection. This article explains IP codes and common Ex markings, and the order in which to check them.
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