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LTH ProcessProbe

Product News Monday, September 13, 2010: Temperature Controls (Pty) Ltd.

LTH Electronics have designed a dissolved oxygen sensor for the process industries. This ProcessProbe™ has been designed with a robust reinforced membrane, it has a simple cartridge membrane replacement, it has flat face obstruction less measurement and proven performance. Waste treatment, sewerage aeration, rivers, reservoirs and boreholes area ideal applications for this instrument.

The construction of the ProcessProbe™  dissolved oxygen sensor provides a measurement system that is ideal for the use in variable flow conditions or applications of extended duration. The sensor comprises of a silver anode tube positioned over a glass rod into which is fused the platinum cathode. The tip pf the glass rod is ground to a precise hemispherical curve that supports the membrane and the cathode.

With most oxygen sensors the output is lower in stagnant solutions than in agitated ones. This is due to the sensor consuming oxygen and creating a depletion layer in the proximity of the cathode. In a stagnant solution if the sample is not updated faster than the sensor, consumes the oxygen a lower output results. A high degree of low dependence occurs with sensors that have large cathodes or thin and highly permeable membranes.

The membrane construction of the ProcessProbe™ consists of thin PTFE layer and a relatively thick steel mesh reinforced silicon layer. The silicon layer is highly permeable to oxygen and provides and oxygen reservoir. The double thick PTFE/silicon membrane therefore acts as an effective buffer against disturbances caused by flow variation. This provides a robust membrane assembly, which has virtually no flow dependence.

For simple maintenance the membrane is supplied as a cartridge, which is held in place by a screw-on sleeve. The cartridge is filled with electrolyte and entrapped air is forced out when it is gripped between the thumb and forefinger.