Oxygen Probe

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What is a Dryden Aqua Oxygen Probe?

The Dryden Aqua  Oxygen Probe is a high performance and extremely robust oxygen probe for the measurement of oxygen in water and air. The probe provides for a low cost, easy maintenance sensor. Our probe is accurate down to 10ppb (0.01mg/l), and is as stable and as accurate as an optical probe but at a fraction of the cost. Also, with the Dryden Aqua Oxygen Probe there is only minimal maintenance required. The probe has a high mv out-put for PLC based controllers, the high out-put increases accuracy and reduces electrical noise problems. The unique shape provides a streamlined approach and minimizes water increases accuracy.

Advantages at a glance

  • Robust construction
  • Stable performance
  • High accuracy
  • Low maintenance

Typical Applications

  • Aquaculture
  • Rivers and lakes
  • Sewerage effluent
  • Industrial waste water treatment systems
  • Hydroponics
  • Many other application where you need to measure oxygen content of a liquid
  • Air quality monitoring, environmental warehouses


Technical Properties

The oxygen probe is a galvanic cell. Basically, the probe acts like a battery in which there are two dissimilar metals in a conducting electrolyte solution. The anode is zinc and the cathode is silver, oxidation takes place on the surface of the anode to form a white deposit of zinc oxide. The rate of oxidation is a function of the diffusion of oxygen through a semi permeable Teflon membrane, which is in turn directly related to the partial pressure of oxygen in solution, or in the air. A potential difference is established in the probe, the milli volt out-put being approx. 8mv per 1 mg/l of dissolved oxygen. This gives the probe a reading of approximately 80mv when in air. Any length of good quality two core (0.5mm squ, multi-strand) cable can be connected to the probe, technically there is no limit to the length of cable that you can attached, however we have only tested to 2000 meters. General maintenance is also very easy, all that you need to do is keep the probe membrane reasonably clean, this is achieved by giving the membrane a wipe with a cloth once a week.

Membranes

There are two types of membrane available for our Oxygen probe. The standard is a Teflon membrane which is temperature compensated in the probe to give very accurate measurements of oxygen in ppm or mg/l. The second type of membrane is made from Polythene and is designed for use with our probe when measuring oxygen in percentage saturation % sat.

The Teflon membrane is slightly better than the polythene membrane and mg/l oxygen measurement are more meaningful than % saturation membranes so we always include Teflon membranes as standard unless requested to provide polythene membranes for % saturation. If you only plan to use % saturation as a measurement then only order the polythene membranes. Teflon membranes sink and %sat polythene membranes float.


Oxygen Probe Specification

  • Two membrane types, mg/l or % sat, mg/l supplied with probe as standard
  • Accuracy: +/- 0.2mg/l
  • Self-temperature compensating from 5 to 40 deg C for 2 & 5 wire probes
  • Very stable, usually 3 to 6 months between calibration checks
  • Heavy duty sub-sea urethane cable, into epoxy sealed internals
  • Diameter = 63 mm, length = 73 mm. Cable length = 5 m (standard)
  • Weight 1000 g incl. cable 5m
  • 6 to 12 mill volt per ppm (mg/l) (depends on temp)
  • Pressure to 10 atmospheres
  • Water flow should be at least 4 cm/sec
  • Response time, to change in, approx 15 to 30 seconds
  • Standard probe is a 2 wire, with temp sensor there are 5 wires
  • Temperature sensor PT100 built in to probe is available as an option, alternative sensors can also be used.

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