19CALIBRATION8. CALIBRATIONPress Menu to enter the main setup menu, use the / keys to highlight Calibration and thenpress Select.8.1. pH PROBE CALIBRATION (HI829113)All calibration data is stored on the probe, allowing probes to be connected to different meters withoutrecalibration.It is recommended to calibrate the instrument frequently, especially if high accuracy is required.More frequent calibrations may be required depending on the type of sample being tested, i.e. turbidbiologically active water samples will require more frequent cleanings and calibrations than cleanerwaters.The probe should be recalibrated:• Whenever the probe is replaced.• At least once a week.• After testing aggressive samples.• After cleaning the sensor.• If “Outside Cal Range” message blinks during measurement (the measurement is outside thecurrent calibration range).• If enabled, when the “CAL DUE” calibration time out message is displayed.pH CALIBRATIONFrom the Calibration menu, use the / keys to highlight pH and then press Select.Calibrate pH allows the user to perform a new calibration using up to three buffers. When a three-point calibration is performed the existing data is overwritten. A single or two-point calibration willuse existing calibration data, if available. Use the / keys to highlight Calibrate pH and thenpress Select.PREPARATIONPour small quantities of the buffer solutions into clean beakers. If possible, use plastic beakers tominimize any EMC interferences. For accurate calibration and to minimize cross-contamination, usetwo beakers for each buffer solution: one for rinsing the electrode and one for calibration.