With the new CeraGel P CPS 71 and TopHit H CPS 471 sensors for the chemical, pharmaceutical and biotechnology industries, Endress+Hauser is believed to offer the only sensor on the market (the CPS 71) with a double-chamber reference system in classical style, ie, 120 mm long and 12 mm shaft diameter.
New gel recipes guarantee the highest protection against contamination and a wide measuring range of 0-14 pH. A membrane has been introduced that meets present and future requirements in process chemistry and pharmaceutical engineering, since observing the specified pH value in production plants guarantees the highest product yields and safe process control.
The aim of the new developments was to exceed the sensor operating times of conventional pH sensors and thereby reduce operating costs. Making IsFET technology available in the TopHit H CPS 471 sensor for pH measurement has opened up new fields of application in the area of biotechnology and in the pharmaceutical and food industries. All sensors from Endress+Hauser are approved in compliance with ATEX and equipped with the TOP 68 connector system. This guarantees safe connection in compliance with IP 68.
Combi electrodes are used in modern process measuring technology, consisting of a glass electrode and a reference electrode. Endress+Hauser has optimised all relevant components of these electrodes, in order to meet customer requirements for low-maintenance sensors. The main emphasis here was on the improvement of the pH-sensitive types of glass, the optimisation of the reference systems and the further development of the gels, which are currently used as electrolytes in the sensors.
The demands on diaphragm glasses are very high. To start with, the response characteristics of the glass should be linear over the entire pH range. The glass should only be sensitive to one type of ion and acid and alkali errors must be small. Good chemical stability should prevail and the diaphragm resistance must not be too high, in order not to increase susceptibility to faults. The linear coefficient of thermal expansion must be similar to that of the shaft glass, so that no strain occurs.
It should be considered that some properties of the glass actually have negative effects, eg, a lower resistance also results in lower chemical stability. With the introduction of the new pH glass, the process has been optimised under all of these viewpoints. Endress+Hauser only makes a distinction between A and B glass. Using these two glasses, it has been possible to introduce new standards that meet the highest requirements and could supersede all conventional pH glasses on the market. Users need only keep two basic sensor types available in stock.
A reference electrode that displays a constant potential, independent of the medium, is required for recording the voltage as a measured value. The quality of the reference system is defined by the consistency of the drainage system, the chemical stability of the reference electrolytes and the type of diaphragm material with regard to susceptibility to blocking and chemical stability. Endress+Hauser's new reference elements consist of a commercially available silver/silver chloride system that is worked into a special, newly developed viscous gel. This has many advantages. The electrodes require little maintenance and no pressurisation is required. Traces of the measuring solution diffusing into the electrode cannot be conveyed to the reference element through confectioning. This guarantees additional protection against contamination of the sensor.
The new CeraGel P CPS 71 pH sensor is equipped with an advanced reference system and can be manufactured with either of the aforementioned diaphragm glass types, as desired. The special design of the sensor makes it possible for it to be used under the hardest conditions. A special feature here is that the reference has double protection, due to a second chamber that is filled with a gel of lower viscosity.
The improved gels permit the sensor to be used at pressures up to 1 MPa. Under such pressure, a maximum process temperature of 100°C should not be exceeded. Intruding media does not endanger the sensor because the gels are particularly chemical-resistant and the additional electrolyte chamber protects the reference system. The IsFET TopHit H pH sensor from Endress+Hauser is made completely of PEEK, down to the ion-sensitive field-effect transistor. The sensor features high mechanical stability and longer calibration intervals. The result is a net reduction of the operating costs of the pH measuring point.
The sensor can be mounted horizontally and overhead. This allows measurement in positions that were previously not possible. The sensor can be installed in all standard retractable assemblies from Endress+Hauser. All the common commercial connection schemes are available for the sanitary sector. The sensor is operated with the advanced Mycom S CPM 153 transmitter, as well as the all rounder Liquisys M and Mypro transmitters.
For more information contact Grant Joyce, Endress+Hauser, 011 262 8000, [email protected]
| Tel: | +27 11 262 8000 |
| Email: | [email protected] |
| www: | www.endress.com |
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