‘Ion trap’ pH electrode

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A robust pH sensor from Endress+Hauser can now solve the problem of reference contamination commonly experienced during pH measurement in ultra harsh conditions such as mining slurries and paper & pulp applications.

pH measurement within ultra harsh applications that include high solid content poses several challenges. Because of the harmful ions that defuse into the pH electrode reference system and the high solid content, the potential to disable the electrode by blocking the diaphragm under these extreme conditions is high. The surface area of the pH electrode diaphragm therefore needs to be enlarged to avoid blockage. However this increases the risk of reference contamination as the diaphragm is porous and more harmful ions can now enter the reference system of the pH electrode.

Traditionally, these enlarged diaphragms have been made from wood due to its resistance to contamination, but the wooden diaphragm is relatively thick and slows down the electrode’s response time. In most critical applications, slow response times are not acceptable.

A new pH electrode (the Orbisint CPS11D and the Orbipore CPS91D) addresses these issues, combining the advantage of having a contaminant resistant reference, with fast response time and high reproducibility.

Utilizing ‘ion exchange’ technology, the ion trap has been placed in the electrodes’ reference system guarding the silver chloride wire. The ‘ion exchange trap’ intercepts contaminating ions and allows the electrical signal to pass between the chambers without contamination.

The design offers customers a faster and more accurate measurement alternative to pH electrodes with wood diaphragms – in the presence of reference contaminants and high solids content present in paper and pulp; slurries, chemical and mineral leaching applications.

Having been proven in long-term tests, both models of electrode – the Orbisint CPS11D and the Orbipore CPS91D – are available with Memosens technology, whereby the signals are transmitted digitally. Memosens sensors not only store information calibration data, but also fundamentally process the data, and can provide the information to outline a full maintenance regime.

The storage of the calibration data in the sensor means that the electrodes can be cleaned, conditioned and calibrated under optimum laboratory conditions, thereby reducing maintenance time and costs and improving longevity.

Endress+Hauser, 1300 363 707, info@au.endress.com

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