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ABB targets industrial pH measurement with AP300 sensor range

Posted: Monday 28th June 2010

ABB offers a reliable, cost effective solution for most industrial pH applications with its range of AP300 pH/Redox sensors. Combining measurement, reference and temperature compensation elements in a single unit, the AP300 is suitable for a wide range of standard industrial applications including water, food, textiles and chemicals.

The sensor versions available are 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 105oC and 6bar. Within the robust outer casing, the electrolyte is a media-resistant gel, which is faced with PTFE liquid junction. The PTFE junction is ideal for most applications and 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 AP300ís 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 which can then be used to compensate for the effects of temperature to produce a precise pH measurement.

A further level of protection is also afforded by ABBís patented 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 elementís inner wire in place, which can affect the strength of the glass.

The AP300 range is available with ABBís 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 15oC. For applications with higher pH levels and temperatures, ABBís 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:

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