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)