Differential pH sensor features sealed reference cell for long life and stability

pH measurements of brine solutions are required in applications as diverse as electrolysis processes and cheese manufacturing, and have traditionally presented challenges in areas such as inaccuracy and short sensor life. These problems - most of which relate to the reference cell - are caused by a combination of high diffusion potentials at the reference junction, the high temperatures encountered in chlorinated brine related processes, and high ground-loop currents in the pH sensor circuits.

In the SC24 differential pH sensor, the reference cell is hermetically sealed in glass, with no porous junction. No electrolyte is in contact with the process, and so the sensor does not suffer from diffusion potentials. The result is a very stable linear voltage output over a typical range of 2-14 pH. It also means that the sensor will operate successfully with minimal maintenance requirements under conditions of high pressure and temperature, or in the presence of corrosive materials. The only wetted materials are platinum and glass, so the unit has a high chemical resistance as well as being sanitary in use.

As a differential sensor, the SC24 reacts to pH/ORP changes rather than measuring the absolute pH value, As such, it is ideally suited to pH process-control applications where the user is interested in the stability of the pH reading - and hence the consistency of the process and the end product - rather than the exact pH value. Typically, the true pH value is measured offline using a traditional laboratory-type sensor, which is then used for calibration of the SC24.

Because the sensor integrates four functions in one - pH sensing, reference cell, temperature compensation and liquid earth (ORP), the user only has to deal with one sensor and one cable. The unit is designed for 12 mm PG13.5 mounting, and so is compatible with most industrial holders. In addition, the SC24 is the most maintenance free pH sensor in the market today. The sensor can also be used for ORP/Redox and for rH control applications.