User manual EUTECH INSTRUMENTS DISSOLVED OXYGEN PROBE

[. . . ] It is recommended to clean the membrane from time to time to ensure maximum reliability. This enables it to function correctly with liquid movement as low as 2-cm / sec (measured at 7 ppm and 13 o C). The membrane material was specially chosen to ensure a negligible influence of deposits on its surface, when compared with traditional systems. Remember that in any biologically active system, deposits will be found on any surface, including the membrane of an oxygen probe. [. . . ] The probe must have the same temperature as the water or air surrounding it, and must therefore be allowed to attain this temperature before being calibrated. Any robust long-life probe such as the Eutech can take up to an hour to respond to a 10-degree temperature change in air, which only takes 10 minutes in water. Take the probe up from the water, wipe the membrane dry, and hang it in free air, away from direct sunlight. When the probe output is stable adjust the transmitter or electronics connected to give the correct output. Calibration value for systems measuring % saturation The calibration value for systems measuring % saturation is always 100. For these systems, and only for these systems, temperature, barometric pressure and salinity have no influence. Calibration value for systems measuring mg/l (ppm) For these measurements adjustment until the output corresponds to the appropriate value from the calibration tables. The first table at the end of this section shows values for various temperature and air pressures, the other values for various temperatures and salinity at 760 mbar. It is essential to correct for temperature-use the air temperature near the probe. At high altitudes, or for greater accuracy, a correction must be made for pressure. For a simple calibration at low altitudes assume a normal barometric pressure of 760 mmHg. If an accuracy of +/- 0. 5 ppm is sufficient, calibration once a month is more than enough. It is, however, much better to perform one thorough calibration than two quick ones. Give the probe time to stabilize, check the barometer and decide if correction for air pressure is necessary. Check the salinity if your farm is a salt-water facility! 3 3. 2 Maintenance The probe's membrane must be kept free from deposits. All surfaces in a biologically active system will be covered by a film composed mostly of bacteria. This bacteria film acts as a diffusion barrier for the oxygen that must diffuse through the membrane. The membrane must, therefore, be cleaned at regular intervals, the frequency depending on the actual condition. The membrane is strong and not easily damaged, but do not try to scratch it clean with a fingernail!There is no need to exchange the electrolyte regularly as in conventional probes!Other Points Worth Considering Even though the Eutech probe is one of the most robust available, it should be treated carefully. It measures at few thousands of a gram of oxygen, which it must "drag" out of the water around it. [. . . ] If possible, re-calibrate after a day or two. Tighten the cap firmly, but remember that you may have to loosen it yourself the next time the probe needs renovation! We do not recommend that a cap be re-used without replacing the membrane, as the membrane stretches to fit the cathode, and will not fit perfectly a second time. 7 A new membrane can easily be fitted to the cap ­ see the drawing overleaf. The membrane must be flat ­ if it wrinkles remove it and try again with a new one. Neither O-ring nor membrane can be used more than once. 4. 2 Spare Parts The Eutech probe is manufactured from tried and tested parts of the highest quality, so the need for spare parts is minimal. A kit can be purchased containing: A cap mounted with a membrane, an anode, nut and 50 ml of electrolyte. [. . . ]