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Section No 8 <br /> Revision No 0 <br /> Date September 5, 1991 <br /> Page 2 of 5 <br /> 8 1 2 Conductivity Meter <br /> Conductivity meter calibration procedures are in accordance with <br /> manufacturer's instructions <br /> 8 1 3 Water Level Recorder <br /> Water level recorder procedures are in accordance with manufacturer's <br /> instructions <br /> 8 1 4 Dissolved Oxygen Meter <br /> 8 1 4 1 Operation Principles - The calibration procedures presented <br /> for the Dissolved Oxygen Meter pertain to the YSI 5700 series dissolved <br /> oxygen probes YSI 5700 Series probes are polarographic sensors A thin <br /> permeable membrane stretched over the sensor isolates the electrodes from the <br /> environment, but allows oxygen and certain other gasses to enter When a <br /> polarizing voltage is applied across the sensor, oxygen that has passed <br /> through the membrane reacts at the cathode, causing a current to flow <br /> The membrane passes oxygen at a rate proportional to the difference <br /> across it in partial pressure of oxygen Since oxygen is rapidly consumed at <br /> the cathode, it can be assumed that the oxygen pressure under the membrane is <br /> zero Hence the force causing the oxygen to diffuse through the membrane is <br /> proportional to the partial pressure of oxygen outside the membrane As the <br /> oxygen partial pressure varies, both the oxygen diffusion through the <br /> membrane and the probe current will change proportionally <br /> i <br /> 8-2 <br />