SOP FOR CALIBRATION OF WEIGHING BALANCE

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OBJECTIVE:-

TOASSURE THE WEIGHING BALABNCES BEING IN THE MANUFACTURING ACTIVITIES CONFIRM TO THE SPECIFIED ACCEPTANCE CRITERIA.

CALIBRATION SHALLBE PERFORMED AS:–

  1. ASPER SPECIFIED FEQUENCY.
  2. FOR NEW BALANCE DURING INSTALLATION.
  3. AFTER ANY MAJOR REPAIR OR COMPONENT REPLACEMENT.

PROCEDURE:–

  1. ENSURE THAT THE WEIGHING IS PROPERLY CLEANED AND LEBELLED.
  2. OPERATE THE BALANCE ASPER RESPECTIVE SOP.
  3. FOR CALIBRATION BALANCES ARE TO BE SUBJECTED FOR THE FOLLOWING TESTS.
  1. LINEARITY TEST
  2. ECCENTRICITY TEST.
  • MEASUREMENT OF UNCERTAINTY (RANDOM PLUS SYSTEMATIC ERROR).

LINEARITY TEST: —

DIVIDE THE FULL SPAN OF BALANCE INTO 5 PARTS AND CONSIDER THE 5 PARTS AS STANDARD WEIGHTS FOR CALIBRATION.

1ST PART – ZERO

2ND PART – 25% OF FULL RANGE.

3RD PART – 50%OF FULL RANGE.

4TH PART – 75% OF FULL RANGE.

5TH PART – 95% OF FULL RANGE.

  1. PLACE THE WEIGHTS ON THE BALANCE ONE BY ONE IN INCREASING ORDER FOR THE 5 DIFFERENT STANDAR RANGES.
  2. REMOVE THE WEIGHTS IN THE REVERSE ORDER FROM THE BALANCE.
  3. CHECK THE DIFFERENCE B/W THE RESPECTIVE WEIGHTS OBSERVED IN BOTH THE ORDER FOR ANY INDIDUAL SET WEIGHT LIMIT.

ECCENTRICITY TEST :–

    1. PERFORM THE TEST USING ONE QURTER WEIGHT OF THE CAPACITY OF THE BALANCE.
    2. PLACE THE SELECTED WEIGHTS ON THE PLATEFORM AT 5 LOCATIONS AS ILLUSTRATED.

MEASUREMENT OF UNCERTAINTY (RANDOM PLUS SYSTEMIC ERROR):–

  • THE WEIGHTS TO BE USED FOR TEST SHALL BE THE SINGLE MAXIMUM WEIGHT AVAILABLE NEAREST TO THE CAPACITY OF THE BALANCE.
  • PLACE THE WEIGHT ON PAN/PLATFORM OF THE BALANCE.
  • RECOPRD THE WEIGHT DISPLAYED.
  • REMOVE THE WEIGHT AND AGAIN PLACE THE WEIGHT ON THE PAN AND RECORD THE DISPLAY ONCE AGAIN.
  • REPEAT THE ABOVE OPERATION OF TEN READINGS AND RECORD THE OBSERVATIONS.
  • CALCULATE THE STANDARD DEVIATION OF TEN READINGS. CALCULATES MEASUREMENT UNCERTAINTYAS GIVEN BELOW—
  • MEASUREMENT UNCERTAINTY = RANDOM ERROR +SYSTEMIC ERROR  X 100/ACTUAL WEIGHT
  • RANDOM ERROR = 3 X STANDARD DEVIATION   (n = 10)
  • SYSTEMIC ERROR = OBSERVED WEIGHT (AVERAGE) – ACTUAL WEIGHT.

ACCEPTANCE CRITERIA –

LINEARITY TEST—THE DIFFERENCE IN DISPLAYED WEIGHT FOR ANY SET OF WEIGHTS DURING INCREASING & DECREASING ORDER SHALL BE NOT THAN PLUS –MINUS 2 LEAST COUNTS OF THE BALANCE.

ECCENTRICITY TEST –

THE DISPLAYED WEIGHTS  SHALL NOT BE MORE THAN PLUS –MINUS LEAST COUNTS FROM THE STANDARD WEIGHT.

MEASUREMENT OF UNCERTAINITY (RANDOM PLUS SYSTEMIC ERROR)—

  • THE STANDARD DEVIATION OF THE TEN CONSECUTIVE READINGS SHALL NOT BE MORE THAN ONE LEAST COUNT.
  • THE MEASUREMENT UNCERTAINITY SHOULD NOT BE MORE THAN PLUS –MINUS 0.1%.