Product category:
Waste-water handling, monitors + treatment
News Release from: Partech Instruments | Subject: Oxyguard
Edited by the Processingtalk Editorial
Team on 28 June 2006
The Partech approach to measuring
Dissolved Oxygen
Measurement of Dissolved Oxygen (DO) in wastewater treatment is essential, but requires robust probes that give high accuracy results and long service life
Measurement of Dissolved Oxygen (DO) in wastewater treatment is essential, requiring robust probes that give high accuracy results and long service life Partech continues to offer Dissolved Oxygen monitoring systems that meet this need, without the complexity of the recently revived optical sensors
This article was originally published on Processingtalk on 23 Nov 2004 at 8.00am (UK)
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The Partech Dissolved Oxygen Systems utilise the Oxyguard sensor, a rugged electrochemical probe that combines a strong HDPE membrane with a unique electrolyte to provide excellent long term stability without the need for routine sensor replenishment or replacement.
Electrochemical cells are fundamentally an electrical circuit, comprising an anode and a cathode in electrolyte, sitting behind a gas permeable membrane.
As the oxygen diffuses through the membrane a chemical reaction takes place that changes the electrochemical balance of the cell in a manner that is proportional to the amount of oxygen present in the sample.
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The design of the Oxyguard sensor means that the electrochemical reaction does not consume the electrolyte or anode, thereby giving it an extremely long operating life.
Partech operational experience has been that the sensor will operate for well in excess of 2 years without replenishment.
The only manual intervention needed is periodic calibration and cleaning.
"When compared with the best electrochemical sensors, the optical Dissolved Oxygen sensors offer no operational benefit," comments Angus Fosten of Partech Instruments: "Indeed, an optical sensor needs to be protected from UV light during calibration to avoid premature failure, and ageing of the optical circuit will mean that frequent calibration will have to be performed at varying intervals.
In addition, the sensor cap will have to be replaced, a procedure that entails maintenance personnel removing the unit from its operating location".
When assessing the relative attractions of the currently available Dissolved Oxygen sensors it is important to include all the elements that contribute to cost of ownership.
The Partech systems need very little expenditure over many years when compared to yearly replacement of membranes or capsules in alternative systems.
Partech is offering its Dissolved Oxygen system with a choice of transmitters: the 840 loop powered transmitter with local display and 4-20mA output; the 810 mains or DC powered transmitter with 4-20mA output and single relay; and the WaterWatch 2420, a fully featured microprocessor monitor with 4-20mA output, two relays and control algorithms.
To make installation of the Oxyguard probe as easy as possible, and to help achieve the best possible results, Partech recommends using its Pioneer Probe holder.
This places the sensor approximately 300 mm below the surface away from the effects of rain, sunshine and fouling by floating debris.
The flexible joint in the mounting shaft allows the sensor to move, providing an anti-fouling and anti-ragging action.
Any fatty deposits build up on the water surface above the probe, so do not disturb the measurement.
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