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M <br /> meter to sound. This point is usually clearly visible on the probe, If it is not visible it should d <br /> located by dipping the probe into a water container where the contact'Can be clearly seen, then- f <br /> marked. The total length of the water level meter should correspond with the length of the <br /> measuring tape. In addition, the individual on the cable should cormspond with <br /> the <br /> correct footage. If the cable does not match the measuring-tape then the difference(!f consistent) <br /> should be calculated. as a percentage, (Le, 100 foot cable measures 102. feet = 984%).. All <br /> measurements with the cable should-then multiplied by 0.98 to correct for the error. if the <br /> individual footage marks are not placid corr y and are not consistent in their, deviation, the <br /> instrurnent should be replaced. <br /> If the water level indicator is constructed of a cable then calriaration will be peiformed once per <br /> year. If there is a discrepancy, the conversion factor will be marked directly can the instrument <br /> Water level indii;ators constructed of tape are more subject to stretching and should be'calibrated <br /> every 6 months and marked with the appropriate conversion,. <br /> Caliibration data for each instrument will be.=corded-aid kept;in a.binder at the:office forfataue. _ -- <br /> reference. The most recent calibration results will also be rccorded in the technicians field notes <br /> Them is no specific farm for water level indicator calibratiorL <br /> '_ <br /> H _Meter <br /> pH is subject to significant variations due tot . . buffering capacity of the water, and <br /> instru:tnent drift-For this reason pH meters must 'brate before and after sampling on each.. <br /> day,and at least once more during the day, To cabibrate a pH meter the instrument reading is <br /> adjusted to rrad correctly for solutions with a pH. <br /> Standard solutions are mixed frosh, according to package instructions,-for eater sampling-event. <br /> Standard solutions or powders for pH 4,7, and 10 am commercially le. These standards <br /> .arc purchased fivsh and-discarded after shelf life has wTired. Shelf lives vary depending on the <br /> brand of standards used. if pm-psolution is used,the expiration date of the solution will <br /> be noted on the c aMration log. <br /> Although different brands of pH meters vary, calibration pmcedt= are similar for all of them.- <br /> A geaerali calibration p follows: <br /> I. Turn on the instrument,check the ba=Y.and 91low to warm up if necessary;. _- <br /> 83949*F'0It23 f 4R3ZS A_Z JWy 14,200 <br />