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meter to sound. This point is usually cleaiiy visible on the probe. If it is not visible it should i located by dipping the probe into a water container where the contact-can be clears E y seen, then marked. The total-length of the water level meter should correspond with the length of the measuring tape. In addition, the individual marks on the cable should correspond with the comet footage. If the cable does not match the measuring tape then the difference Cif'consisteut) should be calculated_ as a percentage, (i.e.; If10 foot cable measures 142 feet = 9$1%),- All measurements with the-cable should-then be multiplied by 0.48 to correct for the error. if the individual footage marks are not placed correctly and arc not consistent in their deviation, the instrument should be replaced If the water level indicator is constructed of a cable then calibration wiII be peifo=ed 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 becalz'brated every 6 months and marked with the appropriate conversion,. Calibrari®n data for each instrument will.bc-recorded-and keptin a binder-at the:office forfuture_ : - reference. The,most recent calibration results will also be recorded in the technicians field notes There is no specific form for water level indicator calibration. off Meter pH is subject to significant variations due to temperature, buffering capacity of the water, and instrument drift. For this reason pH meters must be-calibraud.before and after sampling on each.. day and at lest once mora during the day, To calibratea pH meter the instrument reading is - adjusted to read correctly for solutions with a standard pig. Standard solutions are mined fresh, according to Package 'anis,-for each sampling-event. Standard solutions or powdans for pH 4, 7, and 14 are commercially available, ?hese standards -arc purchased fiesh and-discarded after shelf life has Shelf lives vary depending on the brand of standards used. If preTreparcd solution is used,the egiration date of the solution will be noted on the calibration log. Although different brands of pH meters vary, calt`bration pro-cc&= are similar for all of them- A gencialized calibration p follows: 1. Turn on the instruinent,check the battzY,and allow to warm up if n .'. 83849-F011231OR32i A-2 July 14,2044 2aoo tti1E.�tFet4a,tae. - .