横河SR20-AC52玻璃电极  PH计SR20-AC52横河

SC21D-AGP26      SM21-AG6    

SC21D-AGP64      SM21-AE2     SR20-AS52

                   SM21-AS4     SR20-AC32

SB20-VC               SM21-AS6     SR20D-AS52

SB20-VP         SM21D-AG2  SR20D-AC32

SB20-VS         SM21D-AG4  SR20D-AC22

                   SM21D-AG6  SR20D-AP24

SM23-AN4         SM21D-AL4   SR20D-AP26

SM23-AN6         SM21D-AL6

SR20

SR20 Single Reference Electrodes （non-flow）

The selection of the correct type of junction of a reference electrode depends on the process conditions under which this electrode has to function. The following junction types are available: 1. Ceramic junction.

2. Glass sleeve capillary element.

3. P.T.F.E. junction.

The purpose of the junction is to maintain contact between the reference system in the electrode and the process liquid. When selecting the correct junction, consideration has to be given to ensure that the process liquid does not penetrate into the electrode causing poisoning and a consequential unstable liquid junction potential.

With the first two types of junction, listed above, the KCI solution flows slowly into the process. The flow rate is dependent on the over-pressure in the electrode and on the process temperature. The electrolyte flow rate increases with increasing temperature.

For use in very dirty liquids a glass sleeve capillary element is preferred because of its larger flow surface. The sleeve can be easily cleaned by first moving the ground ring upwards and then wiping the ground faces. Non-flowing reference electrodes with a porous P.T.F.E. junction can also be used in many dirty liquid applications. The dirt resistant properties of P.T.F.E. will prevent complete fouling of the diaphragm.

A non-flow type reference electrode can be used for processes that don’t contain components that poison the reference system. The gel-type electrodes have a large area of porous PTFE junction for optimal resistance against electrode pollution. The SR20-AP26 electrode is the optimal choice for processes that cannot stand contamination with KCl. The SR20-AC22 electrode has a flexible PTFE tube. Therefore this electrode can be applied in processes with frequent temperature- and pressure fluctuations.

Features

• Easy maintenance.

• No reference liquid wastage.

• Maximum process pressure: 1000 kPa （10 bar）.

• High quality Ag/AgCl reference system （pin）

which can stand high temperatures

Additional features of types SR20（D）-AC22

• Temperature / pressure variation compensation.

• To be used in non-polluting fluids.

• Saturated KCl-solution （pellets）.

• For low ionic applications and high temperatures.

• Temperature range: 0 to 120ºC.

• Diaphragm resistance （25ºC） <5kΩ.

Additional characteristics of type SR20（D）-AP24

• General purpose PTFE diaphragm electrode.

• Large PTFE diaphragm.

Additional characteristics of type SR20（D）-AP26

• When KCl is prohibited in the application.

• Double junction, thickened KNO3 in buffer compartment.

• Large PTFE diaphragm against pollution.

Specifications Single Reference Electrodes （non-flow）

* In application where high process temperature occur together with very low （<2） or very high （>12） PH levels the lifetime is shortened.

SR20 Single Reference Electrodes （flow）

Pressure compensated Reference Electrode

In processes with pressure variations, the composition of the electrolyte may change as a result of process liquid penetration into the electrode. Any change in composition of the electrolyte may cause a measuring error or even poisoning of the reference system of the electrode. To alleviate this problem, the electrode with an integral pressure compensation system （“Bellomatic” -type electrode”） may be the solution.

Reference electrode

• Flowing type sensors for dirty applications or （Ultra） pure water applications （often needs a electrolyte reservoir）

• Non-flow type sensors for all general applications

• Ceramic and PTFE junction : electrolyte flows slowly into the process. PTFE resists dirt

• Glass sleeve : very dirty applications or for （Ultra） pure water applications because of the larger flow-rate

Features

• Liquid flow output preventing diaphragm fouling and poisoning the reference system.

• High quality Ag/AgCl reference system （pin） which can stand high temperatures and temperature fluctuations.

• Standard 3.3 m. KCl electrolyte, at temp. above 70ºC thickened electrolyte is advised.

• Automatic compensation for process pressure variations.

• Chemical resistant Viton Bellow material.

• Constant flow of reference liquid, independent of the process pressure variations for minimal diffusion potential.

• Suitable for pure water applications and for polluting fluids.

• Refillable, large KCl reservoir.

Note:

The flow is highly dependent on temperature. When using

the electrode continuously at temperature over 70ºC it is

recommended to fill the electrode with a reference liquid

having a higher viscosity, ordernr. K1520VN （3.3 m. KCl）.

The electrode function is as follows:

The electrolyte vessel of the electrode contains a bellow which is compressed in the working position. One side of the bellow is connected to the pressure via the ceramic junction and at the other side via the inner tube. The pressure inside the bellow equals the pressure outside and only the elasticity of the bellow itself causes the over-pressure which results in a flow of electrolyte. When the bellow is fully “expanded” the electrolyte is exhausted and refilling is required. The bellow must be compressed before refilling.

The refillable reference electrodes have a positive flow of electrolyte to prevent junction fouling or poisoning of the reference system. To prevent penetration of the process liquid into the electrode the pressure in the electrode must be higher than the process pressure. The ceramic junction is suitable for most applications. In strong polluting processes a sleeve junction is preferable.

Specifications Single Reference Electrodes （flow）

3） The flow is highly dependent on temperature. When using the elctrode continuously at tempratures over 70°C it is recommended to fill the electrode with a reference liquid having a higher viscosity （ordernr. 82895203 and 82895258）

PH计，是一种常用的仪器设备，主要用来精密测量液体介质的酸碱度值，配上相应的离子选择电极也可以测量离子电极电位MV值，广泛应用于工业、农业、科研、环保等领域。该仪器也是食品厂、饮用水厂办QS、HACCP认证中的*检验设备。
 人们根据生产与生活的需要，科学地研究生产了许多型号的酸度计：
按测量精度
可分0.2级、0.1级、0.01级或更高精度。
按仪器体积
分有笔式（迷你型）、便携式、台式还有在线连续监控测量的在线式。
根据使用的要求
笔式（迷你型）与便携式pH酸碱度计一般是检测人员带到现场检测使用。
选择pH酸碱度计的精度级别是根据用户测量所需的精度决定，而后根据用户方便使用而选择各式形状的pH计。
◆按便携性分的，分为：便携式pH计，台式pH计和笔式pH计。
◆按用途分为：实验室用pH计，工业在线pH计等。
◆按*程度分为经济型pH计，智能型pH计，精密型pH计或分为指针式pH计，数显式pH计。
◆笔式pH计，一般制成单一量程，测量范围狭，为简便仪器。
便携式和台式pH计测量范围较广，常用仪器，不同点是便携式采用直流供电，可携带到现场。实验室pH计测量范围广、功能多、测量精度高。
工业用pH计的特点是要求稳定性好、工作可靠，有一定的测量精度、环境适应能力强、抗*力强，具有模拟里量输出、数字通讯、上下限报警和控制功能等。
什么是pH？pH是拉丁文“Pondus hydrogenii”一词的缩写（Pondus=压强、压力hydrogenium=氢），用来量度物质中氢离子的活性。这一活性直接关系到水溶液的酸性、中性和碱性。水在化学上是中性的，但不是没有离子，即使化学纯水也有微量被离解：严格地讲，只有在与水分子水合作用以前，氢核不是以自由态存在。
H2O+ H2O=H3O+ + OHˉ
  显示控制仪
由于水合氢离子（H3O）的浓度是与氢离子（H）浓度等同看待，上式可以简化成下述常用的形式：
H2O=H+ + OHˉ
此处正的氢离子人们在化学中表示为“H+离子”或“氢核”。水合氢核表示为“水合氢离子”。负的氢氧根离子称为“氢氧化物离子”。
利用质量作用定律，对于纯水的离解可以找到一平衡常数加以表示：
K=H3O+×OH————H2O
由于水只有极少量被离解，因此水的克分子浓度实际为一常数，并且有平衡常数K可求出水的离子积KW。
KW=K×H2O KW= H3O+·OH－=10－7·10－7=10－14mol/l（25℃）
也就是说对于一升纯水在25℃时存在10－7摩尔H3O+离子和10－7摩尔OHˉ离子。
在中性溶液中，氢离子H+和氢氧根离子OHˉ的浓度都是10－7mol/l。如：
假如有过量的氢离子H+，则溶液呈酸性。酸是能使水溶液中的氢离子H+游离的物质。同样，如果使OHˉ离子游离，那么溶液就是碱性的。所以，给出H+值就足以表示溶液的特性，呈酸性还是碱性，为了免于用此分子浓度负冥指数进行运算，生物学家泽伦森（Soernsen）在1909年建议将此不便使用的数值用对数代替，并定义为“pH值”。数学上定义pH值为氢离子浓度的常用对数负值。即pH=-log[H+]。
因此，pH值是离子浓度以10为底的对数的负数：
改变50m3的水的pH值，从pH2到pH3需要500L漂白剂。然而，从pH6到pH7只需要50L的漂白剂。
测量pH值的方法很多，主要有化学分析法、试纸法、电位法。现主要介绍电位法测得pH值。
电位分析法所用的电极被称为原电池。原电池是一个系统，它的作用是使化学反应能量转成为电能。此电池的电压被称为电动势（EMF）。此电动势（EMF）由二个半电池构成，其中一个半电池称作指示电极，它的电位与特定的离子活度有关，如H+；另一个半电池为参比半电池，通常称作参比电极，它一般是测量溶液相通，并且与测量仪表相连SR20-AP26。
例如，一支电极由一根插在含有银离子的盐溶液中的一根银导线制成，在导线和溶液的界面处，由于金属和盐溶液二种物相中银离子的不同活度，形成离子的充电过程，并形成一定的电位差。失去电子的银离子进溶液。当没有施加外电流进行反充电，也就是说没有电流的话，这一过程zui终会达到一个平衡。在这种平衡状态下存在的电压被称为半电池电位或电极电位。这种（如上所述）由金属和含有此金属离子的溶液组成的电极被称为*类电极。
此电位的测量是相对一个电位与盐溶液的成分无关的参比电极进行的。这种具有独立电位的参比电极也被称为第二电极。对于此类电极，金属导线都是覆盖一层此种金属的微溶性盐（如：Ag/Agcl），并且插入含有此种金属盐阴离子的电解质溶液中。此时半电池电位或电极电位的大小取决于此种阴离子的活度。
此二种电极之间的电压遵循能斯特（NERNST）公式：
  能斯特公式
式中：E—电位
E0—电极的标准电压
R—气体常数（8.31439焦耳/摩尔和℃）
T—开氏温度（例：20℃相当于（273.15+20）293.15开尔文）
F—法拉弟常数（96493库化/当量）
n—被测离子的化合价（银=1，氢=1）
ln（aMe）—离子活度aMe的对数
标准氢电极是所有电位测量的参比点。标准氢电极是一根铂丝，用电解的方法镀（涂覆）上氯化铂，并且在四周充入氢气（固定压力为1013hpa）构成的。
将此电极浸入在25℃时H3O+离子含量为1mol/l溶液中便形成电化学中所有电位测量所参照的半电池电位或电极电位。其中氢电极作为参比电极在实践中很难实现，于是使用第二类电极做为参比电极。其中zui常用的便是银/氯化银电极。该电极通过溶解的AgCl对于氯离子浓度的变化起反应。
此参比电极的电极电位通过饱和的kcl贮池（如：3mol/l kcl）来实现恒定。液体或凝胶形式的电解质溶液通过隔膜与被测溶液相连通。