TROLL 9500 Operator's Manual - Geotech Environmental Equipment

Section 13: Dissolved Oxygen—OpticalCalibration Solutions100% DO calibration is performed in water saturated with air. For bestresults, use the In-Situ RDO Bubbler Cal kit (Cat. No. 0048580).0% DO calibration is performed in an oxygen-depleted solution. Sodiumsulfite (Na 2SO 3, Catalog No. 0017670) is available from In-SituInc. Bubbled nitrogen may be used; in this case allow plenty of timefor the oxygen to be completely purged from the water.Recommended Calibration FrequencyCalibration frequency is more predictable than with electrochemical DOsensors, since the sensor does not drift appreciably. If the foil is not mechanicallydamaged or removed, calibration can last three months or more.TIP: For best results, check the RDO sensor several timesper year in 100% air-saturated water.Traditional 2-Point CalibrationIdeally, the RDO sensor should be calibrated under stable and controlledconditions, like those found in a laboratory setting. However,field calibration can also be performed. Calibration solutions should beclose in temperature to the sample matrix.One or two calibration points can be taken. If only one point is taken,the software uses the results of a previous calibration for the other point.Allow 5-10 minutes for temperature and oxygen equilibration.TIP: The equilibration time depends on the condition of thewater with respect to temperature and exposure to air.2. Connect the TROLL 9500 to a PC and establish a connection inWin-Situ 4 or Pocket-Situ 4. Win-Situ screens are illustrated here.The Pocket-Situ interface is similar, with the Navigation tree at thetop and the Information pane below it.3. Select the TROLL 9500 in the Navigation tree. The software willautomatically detect and display the installed sensors.4. Select Rugged Dissolved Oxygen in the Parameters list.Information on the RDO sensor is shown, including its serial number(SN), the foil batch number, and recent calibration information,as shown in the large screen at the bottom of the page.5. Select Calibrate.6. Before the RDO Calibration Wizard starts, you will be asked howyou want to handle barometric pressure. See the sidebar onpage 93.A 2-point calibration (100% and 0%) is recommended• When you expect to measure very low DO values (< 5 mg/L),• When required by Standard Operating Procedures,• After replacing the sensor caplOxygen Saturation Point1. Submerge the RDO sensor in a container of clean water aeratedwith the In-Situ bubbler. Ensure that the sensor is completelysubmerged and the sensor cap is not directly in the bubble stream.Full Screen buttonTIP: To see all of the informationpane, you can clickthe “Full Screen” button onthe Win-Situ toolbar.45Device clockTROLL 9500 Operator’s Manual 920095110 rev. 007 01/09