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M <br /> f meter to sound. This point is usually clearly visible on the probe. If it is not visible it should k� <br /> located by dipping the probe into a water container <br /> where the contact can be cl <br /> early seen, then j <br /> marked. The total length of the water level meter should correspond with the Icngth of the <br /> measuring tape. In addition, the individual marks on the cable should correspond with the <br /> correct footage. If the cable does not match the measuring tape then the difference <br /> Of consistent) <br /> should be calculated• as a pez,6eiitage, (Le.; 100 foot cable measures IOZ feet � 98°/®). All <br /> measurements with ibe cable should-then be multiplied by 0.98 to correct for the error. If the <br /> individual footage marks are not placed correctly, and arc not consistent in their deviation, the <br /> initrument should be replaced. <br /> If the water level indicator is constructed of a cable then calt-bration will be peirformed once per <br /> year. If there is a discrepancy, the conversion factor will be marked directly on the instrument: <br /> Water level indicators constructed of tape are more subject to stretching and should be calibrated <br /> every 6 months and marked with the appropriate conversion.. <br /> Calx`bration data for each instrument will.be-recorded.and kcptin-a.binder•at the:office foa-futnre_ - <br /> reference, the most recent tah1 ration results will also be recorded in the tecimiciaM field nates. <br /> Thverc is no specific faun for water level indicator calibration. <br /> RH Meter <br /> pH is.subject to significant variations due to temp, buffering capacity of the water, and <br /> cat drift. For this reason pH meters,must be-cafilrated before and after sampling on each.. <br /> day and at least once more during the day, To calibrate a pH meter the went reading is _ <br /> 411sted to read correctly for solutions with'a standard yl-L <br /> standard solutions are mixed fresh, according to PackAge ' ',Oris,•far each camp -event.' <br /> Standard solutions or powders for pH 4,-7. and 10 are COMUlatially available. That standards <br /> arc PMMhased fresh and'discarded err shelf life has lives vary dcpeading on the <br /> brand of standards used. If pre-prepared solution is used,the arpiration lotto of the solution wilt <br /> be noted on the calibration Iog< <br /> Afthough different brands of pH meters vary, calibration procedures are similar for allof them.- <br /> A gen c ali'bradon p follows: <br /> 3. Turn on the instrument,check the battay.and allow to warm up if necessary, <br /> 93949•FO IM I ORW A-2 hey 14,2000 <br />