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SOP for Operation and Calibration of Field Water Quality Instruments 3 <br />4. Record calibration information in the monthly calibration record kept in the office. Information to be <br />recorded includes all calculations, readings taken during calibration, adjustments made to meter, date <br />of calibration, and accuracy prior to calibration. <br />3.3.2 Field Operation <br />1. Perform a battery check each day prior to calibration. <br />2. Immerse probe -end of meter into sample. Allow time to equilibrate to a stable reading (f 10 %) and <br />record value. Sample may need to be stirred to ensure consistent reading. <br />3. When recording reading, be sure to record any scale factor (i.e., x 1,000 µS) used in obtaining the <br />value. It is advised to record the actual meter reading with the scale factor, rather than perform <br />calculation prior to recording value. <br />4. Rise probe with deionized or distilled water and cover with water - filled cap or place a moist wet <br />tissue inside the cap. <br />3.4 Dissolved Oxygen Meter <br />Dissolved oxygen (DO) meters are available from several manufactures. Whetstone commonly uses the <br />YSI® 550A, which is a reliable and relatively durable field instrument. The information provided below is <br />directly applicable to the YSI® 550A, and may be generally relevant to other DO meter makes and models. <br />3.4.1 Calibration <br />The DO meter will be calibrated as instructed in the instrument manual. Calibration details will be documented <br />in the fieldbook. The condition of the probe will be checked prior to each measurement. <br />1. Turn on the meter and allow 15 minutes of warm up time before calibration. <br />2. Ensure that the sponge inside the probe chamber is moist. <br />3. Shake or blow off excess water on the sensor. Check for fouling or damage to the sensor, especially <br />check for holes or tears in the membrane. Check for air bubbles beneath the membrane. Replace the <br />solution and membrane if any of the above exists. If you need to replace the membrane, ensure that <br />membrane housing has been filled with KCL fluid for at least 12 hours before first use. <br />4. Insert the sensor into the probe chamber. <br />5. On the calibration log record date, time, analyst, warm up time, probe temperature, altitude where you <br />are, and stabilized pre - calibration DO in mg/1 (press the MODE button to change from percent ( %) <br />saturation to mg/1). <br />6. To enter the calibration menu use two fingers to press and release both the UP ARROW and DOWN <br />ARROW keys at the same time. <br />7. The meter will say CAL on the screen in large letters and CAL in small letters in the lower left corner. <br />These small CAL letters will stay on the screen until the calibration process is done. <br />8. Press ENTER. <br />9. The meter will show the altitude (x100) in feet. Adjust the altitude with the up and down arrow buttons <br />for the elevation where the calibration is taking place. <br />10. Press ENTER. <br />11. The % saturation value is now on the screen. <br />12. Press ENTER. <br />4153A.140129 Whetstone Associates <br />