水质分析仪的工作原理
Working principle of water quality analyzer
污水处理厂使用的分析仪有两种：pH计和溶氧分析仪。
There are two types of analyzers used in sewage treatment plants: pH meters and dissolved oxygen analyzers.
1、pH计的工作原理 水的pH值随着所溶解的物质的多少而定，因此pH值能灵敏地指示出水质的变化情况。pH值的变化对生物的繁殖和生存有很大影响，同时还严重影响活性污泥生化作用，即影响处理效果，污水的pH值一般控制在6.5～7之间。
1. The working principle of a pH meter is that the pH value of water varies with the amount of dissolved substance, so the pH value can sensitively indicate changes in water quality. The change in pH value has a significant impact on the reproduction and survival of organisms, and also seriously affects the biochemical function of activated sludge, which affects the treatment effect. The pH value of wastewater is generally controlled between 6.5 and 7.
水在化学上是中性的，某些水分子自发地按照下式分解：H2O=H++OH-，即分解成氢离子和氢氧根离子。在中性溶液中，氢离子H+和氢氧根离子OH-的浓度都是10-7mol/l，pH值是氢离子浓度以10为底的对数的负数：pH=-log，因此中性溶液的pH值等于7。如果有过量的氢离子，则pH值小于7，溶液呈酸性；反之，氢氧根离子过量，则溶液呈碱性。
Water is chemically neutral, and some water molecules spontaneously decompose into hydrogen ions and hydroxide ions according to the following formula: H2O=H++OH -. In a neutral solution, the concentrations of hydrogen ion H+and hydroxide ion OH - are both 10-7mol/l, and the pH value is the negative logarithm of the hydrogen ion concentration at the base of 10: pH=- log, so the pH value of a neutral solution is 7. If there is an excess of hydrogen ions, the pH value is less than 7, and the solution is acidic; On the contrary, if there is an excess of hydroxide ions, the solution will be alkaline.
pH值通常用电位法测量，通常用一个恒定电位的参比电极和测量电极组成一个原电池，原电池电动势的大小取决于氢离子的浓度，也取决于溶液的酸碱度。该厂采用了CPS11型pH传感器和CPM151型pH变送器。测量电极上有特殊的对pH反应灵敏的玻璃探头，它是由能导电、能渗透氢离子的特殊玻璃制成，具有测量精度高、抗干扰性好等特点。当玻璃探头和氢离子接触时，就产生电位。电位是通过悬吊在氯化银溶液中的银丝对照参比电极测到的。pH值不同，对应产生的电位也不一样，通过变送器将其转换成标准4～20mA输出。
The pH value is usually measured by the potentiometric method, using a constant potential reference electrode and a measuring electrode to form a primary battery. The magnitude of the primary battery electromotive force depends on the concentration of hydrogen ions and also on the pH of the solution. The factory adopts CPS11 pH sensor and CPM151 pH transmitter. There is a special pH sensitive glass probe on the measuring electrode, which is made of special glass that can conduct electricity and penetrate hydrogen ions. It has the characteristics of high measurement accuracy and good anti-interference. When the glass probe comes into contact with hydrogen ions, a potential is generated. The potential is measured using a silver wire suspended in a silver chloride solution as a reference electrode. Different pH values result in different potentials, which are converted into standard 4-20mA output through a transmitter.