TROLL 9500 Operator's Manual - Geotech Environmental Equipment

Section 10: Monitoring Water Quality: OverviewWhen you select the sensor . . .. . . informationon the lastcalibration isshownHow Often to CalibrateNo sensor will remain in calibration forever. The calibration frequencyis almost completely determined by the chemical properties of thefluid being monitored, and the accuracy you wish to achieve fromthe instrument. For example, when used in relatively clean water, ina normal pH range, at a relatively stable temperature, some sensorscould remain in calibration for a couple of weeks or longer. On theother hand, in surface water with a high nutrient content and widetemperature fluctuations, the sensors may need to be cleaned andrecalibrated every few days. Your own measurement results are thebest guide to the need to recalibrate.pH calibration information for a combination pH/ORP sensor in port 1The calibration reports are accessible from the Tools Menu and theShow Calibration Report button on the toolbar. They may alsobe accessed like other files through Windows Explorer (desktop PC)or File Explorer (PDA); they are not displayed in the Data Folder. Theymay be viewed or printed to provide a complete calibration history.TIP: Here’s how to find the calibration report indexes:Desktop or laptop PC—Calibration Reports subfolder in the folderwhere Win-Situ 4 is installedPDA—Calibration Reports subfolder in the folder where Pocket-Situ4 is installedExample of a calibration report indexFolders:FolderSN32072SN45025Click a folder to see its listingsClick a tile to open itSN32072Files:File NameSN32072 2006-04-17 171530 TURB.htmlSN32072 2006-06-18 102309 DO.htmlSN32072 2006-08-14 134200 QuickCal.htmlSN32072 2006-11-25 121530 PH.htmlSN32072 2007-01-11 154322 Cond.htmlWhen a sensor or instrument is new, we recommend checking thereadings often (say, once a day) to get an idea of the stability of thesensor.Changes in flow also affect readings. Constant flow will increase theaccuracy. This can be achieved with the stirring accessory.The table below may be used as a very general guideline to how longsensors may be expected to remain in calibration under optimumconditions:pH, ORP1-2 monthsConductivity 2-3 monthsD.O. (polarographic) 2-4 weeksD.O. (optical, RDO) up to a year if foil is not damagedISEs1 dayTIP: For additional information on calibration schedules, seethe Technical Note on Instrument Calibration in theDownloads section at www.in-situ.com.How to Check if a Sensor is Still in CalibrationImmerse the sensor in a calibration standard of known value and atthe same temperature as the original calibration. Compare the sensorreading to the solution value. Some drift is to be expected, but generallythe readings should fall within the sensor’s accuracy specification.If readings fall outside the accuracy specification by an amount thatis not acceptable for your current application, recalibration is recommended.You will quickly learn by experience how often you need torecalibrate a given sensor based on usage.TIP: Quick Cal solution may be used for a quick check ofpH, ORP, and conductivity. Refer to the values printed on thelabel.MP TROLL 9500serial numberCal DateCal Time(hhmmss)ParameterTROLL 9500 Operator’s Manual 640095110 rev. 007 01/09