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ABB is offering its range of AP300 pH/Redox sensors for industrial pH applications in the water, food, textiles and chemicals sectors.

The AP300 combines measurement, reference and temperature compensation elements in a single unit.

Versions of the sensor include insertion probe, dip-type immersion and in-line flow-through, enabling users to cover the widest possible range of applications.

Rugged construction enables the sensors to operate at up to 105C and 6 bar.

Within the robust outer casing, the electrolyte is a media-resistant gel, which is faced with PTFE liquid junction.

The PTFE junction is especially resistant to fouling when used in conjunction with a flat glass element.

To help maximise protection against electrode poisoning, the AP300 features a double-junction construction.

This helps to extend the life of the sensor by protecting the reference electrode from poisoning in two ways.

First, the design effectively doubles the length of the diffusion path between the PTFE interface and the electrode, so any poisoning ions from the sample take longer to reach it.

Second, it discourages any movement of the reference gel around the electrode by enclosing it in a pocket.

The AP300’s integral temperature compensator offers improved accuracy and speed of response.

The temperature sensor is located at the tip of the AP300 together with the measuring and reference electrodes.

The sensor provides accurate data that can be used to compensate for the effects of temperature to produce a precise pH measurement.

A further level of protection is provided by ABB’s plug seal technology, which reduces thermal stresses within the pH-sensitive glass electrode.

This method replaces the process of melting the glass during manufacture to hold the element’s inner wire in place, which can affect the strength of the glass.

The AP300 range is available with ABB’s standard pH-sensitive glass or the option of low-resistance glass, which speeds up the response of the sensor by an order of magnitude at temperatures below 15C.

For applications with higher pH levels and temperatures, ABB’s standard glass offers a much lower sodium error than competing products, enabling the sensor to maintain its accuracy even at very high pH levels, when sodium ions would otherwise cause readings to drift.

The use of a three-wire PT100 as standard enables users to be confident in the accuracy of the temperature readings from AP300 units, regardless of the length of cable runs.

There are five models in the AP300 range.

The AP301 is a PVDF, in-line/immersion, locknut-style sensor that can also be converted for dip-type immersion.

The AP302 and AP303 are made from PVDF and can be converted to flow or dip immersion.

The AP304 and AP305 are fully-retractable PVDF-bodied sensors that can be installed, commissioned and maintained without the need for an expensive bypass system.

This can reduce the cost of new projects and enables the sensors to be maintained without shutting down the process.

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