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f meter to sound. This point is usually clearly visible on the probe. If it is hot visible it should k . <br /> -located by dipping the probe into a water container where the contact-can be clearly seezrthen, <br /> marked. The total-length of the water level meter should correspond with the 'length of the <br /> measuring tape. In addition, the individual marks op the cable should correspond with the <br /> correct footage. If the cable does not match the measuring tape then the diff, <br /> rrncc(if consistent) <br /> should be cal+cutated as a percentage, (Le,; 100 foot cable measures 102, feet 9$°/®}. All <br /> measurements with the cable should-then be multiplied by 0.98 to corm for the =or. If the <br /> individual footage marks are not placed correctly and arc not consistent in dneir deviation, the <br /> ent should be replaced. <br /> If the water level indicator is constructed of a cable then c�libration will be perfotmed 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 becalibrated <br /> every 6 months and marked with the appropriate conversion.. <br /> Calibration data for each instrument will-be-recorded-and keptia a-binder at the.office for-future_ - <br /> reference.. The most recent caliibration results will also be recorded in the technicians field es- <br /> There <br /> is no specific farm for water level indicator calibration. <br /> PH Meter <br /> PH is.subject to significant variations due to t«nperat.Urc, buffering capacity Qfthc water, and <br /> cut ddfL For this reason pH metersmust be-calibrated before and alter sampling on each.. <br /> day,and at least once more during the day. To calibrate a pH metes-the instrumc=readingis - <br /> a4usted to read correctly for solutions with a standard plFf. <br /> Standard solutions are mixed.fresh, according to packA8c insuuctioris,-for each sampyng'event, <br /> Standard solutions or powders for pH 4,7, and 10 are wormer i4y avatitable• Thi standards <br /> $repurchased and-discarded after shelf life has WTira Shelf lives vary depending oil the <br /> brand of standards used. If pre-prepired solution is used,the expiration date of the solution wM <br /> be noted on the calibration log. <br /> . Afthough dif rercnt brands of pH meters vary,eal'bration piroccdur;s are similar for alI of them. <br /> A seneial&d calibration procedlijefollows: <br /> i. Turn on the instrument,check the battery,and allow to vmM up if necwsazy.• <br /> 23483849.FO 1k23 f OR325 A-2 fitly 14,2000 <br /> s <br />