19Section 5 MaintenanceDANGEROnly qualified personnel should conduct the tasks described in this section of themanual.Proper maintenance of the measuring windows in the sensor is critical for accuratemeasurements. The measuring windows should be checked monthly for soiling and thewiper checked for wear.Important Note: The seals must be replaced every 2 years by the Service Department. Ifthe seals are not changed regularly, water may enter the probe head and seriouslydamage the instrument.5.1 Maintenance Schedule5.2 Cleaning the Sensor Measuring WindowsCAUTIONAlways wereSafety glasses, Gloves and Overalhandling hydrochloric acid and observe safety regulations.The measuring windows are made of quartz glass. If necessary, they can be cleaned witha cleaning agent and a cloth.Maintenance Task DurationVisual inspection monthlyCheck calibration monthly(depending on the ambient conditions)Inspection six months (counter)Seal change every 2 years (counter)Change wiper and reset counter as per counter (20000 cycles)