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K ® meter to sound. This point is usually clearly visible on the probe. If it is not visible it should located by dipping the probe into a water container where the contact can be clearly seers, then . marked. The fatal length of the water level meter should correspond with the length of the measuring tape. In addition, the individual on the cable- should correspond with the correct footage. If the cable does not match the measuring 'tape then the difference (if consistent) should be calculated_ as a percentage, (Le, 100 foot cable measures 102 feet � 9$°/®}. All measurements with the- cable should -then be multiplied by 0.98 to correct for the error. if the individual footage marks are not placed correctly and are not consistent in their deviation, the instrument should be replaced. If the water level indicator is constructed of a cable then calibration will be peifortned once per year. If there is a discrepancy, the conversion factor will be marked directly on the instrument. Water level indicators constructed of tape are more subject to stretching and should be calibrated every 6 months and marked with the appropriate conversion.. CalliibraLdon data for each instrument will .be -rete -and kegt_ia a .binder. at the: office for -future_ - . reference. The most recent tali'bmtion results wW also be recorded in the technicians field nates. There is .no specific form for water level indicator calibration. _ yH Meter PH is subject to significant variations due to terapm2t.uxe, buffering capacity of the water, and instrument drift. - For this reason pH meters must be- calt'bzated before and after sampling on each.. day ,and at least once more during the day. To calibrate a pH meter the insstrurnent reading is adjusted to read correctly for solutions with a standard pH.. Sbndard solutions aremixed f• ...t wcording to p.cksge insa r«r •r • each rs r revent. 'Standard solutions orpm.Wers forPH 4,7, and +f are cotnmer-ciany■ .. r•. t a • r t. a fresh and- discarded . .t t has wopired. Shelf., vary depending • r the brand • r r . • used. If pre -prepared • r t is usedtheexpiration date of ttsolution will be noted r•: • t the W.• r t t f g. Although different brands of pH meters vary, calibration proccdu= are similar for all of theca A generalized calibration procedure follows: l . Turnon the instrument, check the batietyr and allow to warm up if necessary., 234US49•FO IU31OR32S A -Z Jury 14,200 copnfgx 2000 t kkWer. sac.