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k <br /> meter to sound This point is usually cleaicly visible on the probe. -If it is bot visible it should t ~ <br /> looted by dipping the probe into a water container where the contact *n be clean <br /> Y seen, then- <br /> marked. <br /> hen ed The total length of the water level meter should correspond with the 'length of the <br /> measuring tape. In addition, the individual marks oa the cable should correspond with the } <br /> correct footage. If the cable does not match the measuring tape then the difference(tf consistent} <br /> should be calculated as a percentage, (Le, 100 foot cable measures 182 feet � 98°!®}. All <br /> measurements with the-cable should-then be multiplied by 0.98 to corrxct for the error. If the <br /> individual footage marks arc riot placed correctly and are not consistent in their deviation, the <br /> instrument should be replaced <br /> If the:water level indicator is constructed of a cable then calibration will be p ufo-cmeed once per <br /> year: If there is a disc rgmncy, the conversion factor will be marked direcd_y on the instrument <br /> Nater level indicators constructed of tape are more subject to stretching and should be'calibrated <br /> d <br /> every 6 month and marked with the appropriate conversion. <br /> Calibration data for each instrument will.be-recorded-.and kegtiira binder-at the office for•future_ : - <br /> reference,. The most recent calibration results will also be recorded in the techaicia field notes. <br /> There is.nes specific fon,for water level indicator calibration. <br /> H is 4b'ect to si - <br /> P 3 gnifcant variations due to temperature, buffering capacity of the water, and <br /> fintrument drift.-For this reason pH meters must be-calibrated,before and after sampling on each.. <br /> day and at least once more during the day. To calibrate a pH meter the hnMjment reading is <br /> adjusted to read coa=dy for solutions with a standard pH. <br /> Standard solutions are mixed fresh, according to package instrucxiods,•for each sampling-evcnL <br /> Standard solutions or pounders for pH 4,7, and 10 are commercially available These standards <br /> -are purchased fresh and'discarded after shelf life has expired. Shelf lives vary depeading on the <br /> brand of standards used. If pre-prepared solution is used,the expiration date of the solution will <br /> be noted on the calibration log. <br /> Afthough different brands of pH meters vary, calibration procedures are sirnilar for all of them. <br /> A geneiaLized calibration procedure follows: <br /> I. Turn on the instrument,check the battery,and allow to warm up if neccssmy.. _ <br /> 23.493949•FO IU3 f 0M A-2 *14,x044 <br /> 2M KklCt kWer,lac. E <br /> . 1 <br />