Dissolved Oxygen Probes, galvanic cells
Robust, Accurate, Stable and easy to maintain
The Dryden oxygen probe is a very high performance and extremely robust oxygen probe manufactured by Dryden Aqua for the measurement of oxygen in water and air. The probe provides for a low cost, easy maintenance sensor suitable for connection to Dryden Aqua monitors, or your own instrumentation.
Our probe is accurate down to 10 ppb (0.01 mg/l), and is as stable and as accurate as an optical probe but at a fraction of the cost.
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 stream-lined approach and minimises water turbulence
- Rivers and lakes
- Sewerage effluent
- Industrial waste water treatment systems
- Almost any application where you need to measure the oxygen content of a liquid
- Air quality monitoring, environmental warehouses
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. 8 mv per 1 mg/l of dissolved oxygen. This gives the probe a reading of approximately 80 mv when in air.
Any length of good quality two core (0.5 mm squ, multi-strand) cable can be connected to the probe, technically there is no limit to the length of cable that you can attach, 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.
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.
How to identify the membranes
Teflon membranes will sink when placed in freshwater, Polythene membranes will float. If you use the wrong membrane the temperature compensation will not work properly, especially if the water temperature is very different from the air temperature
DIN rail mounted oxygen transmitter with display
- 1 x oxygen probe per transmitter
- 2 x relay out-puts1 x analogue out-put
- 1 x clip on display
- Din rail mount as many units as you like in an enclosure, supply power 24 v to 230 v ac/dc
By connecting the transmitter to our oxygen probes you have a complete oxygen monitoring and control systems, or you may use the analogue out-put from the transmitters to feed into your own PLC system.
The oxygen transmitter will accept an input directly from our Oxygen Probes. If you want to display and alarm for both oxygen and temperature (PT100 sensors) then two transmitters will be required. The transmitter can be set up to give virtually any analogue out-put that you may want (e.g. 0 to 10 v or 0 to 20 mamps, or 4 to 20 mamps). There are also two programmable relay out-puts and a display.
DIN rail mounted transmitter
You may mount one transmitter next to an oxygen probe for local monitoring and control, or you can locate the transmitter in the control room. You may have up to 2000 m of cable on one of our probes, this is okay, you do not need to locate the transmitter next to the probe. This arrangement then allows you to fit a multiple number of transmitters in the one box, for example you may have up to a 100 transmitters in one enclosure, and then use the analogue out-put to feed into a PLC, computer or data logger.
The transmitters are provided with a clip on front display which is used to program the transmitter for different functions. The display gives the raw data out-put from the oxygen probe. It is useful to display the raw data, especially if you are using PLC based systems. The display can also be used to calibrated the unit to display the data as dissolved oxygen (units will be shown as mv). This makes for a very low cost multi-channel dissolved oxygen Monitor.