SOP for Calibration of Weighing Balance

Aim: To lay down the procedure for calibration of the weighing balance

Scope: This SOP is applicable for calibration of weighing balances used in (area – your area or department)

Responsibility: The user department is responsible for the calibration of balances in their area

Procedure:

Balances are calibrated for accuracy during daily calibration, and accuracy and corner load tests are performed during trimonthly calibration.

Daily Calibration Process:

Daily calibration shall be performed before start of the weighing operation of the day
Ensure the balance is in cleaned state
Level the balance with help of leveling screws until air bubble is in the center.
Now switch on the balance and the display shows zero
Now place the standard weights (50mg,10 g,100 g) for daily calibration and ensure standard weights cover the entire operating range.
Place the weights and record the observation in the daily calibration record one after other starting from lower weights
The variance should not be more than the tolerance limit and if it is out of limit, then do not use the balance.

Trimonthly calibration:

Once in every three months
If any change in balance position
After every major maintenance
Trimonthly calibration is performed for accuracy and corner load test.
Accuracy verification of balance shall be carried out by weighing standard weights covering the entire weighing range of the balance i.e. min and max weights
Corner load test shall be performed by placing standard weights of one third of the maximum capacity in all corners and in the center.
Suppose balance capacity is 500KG so one third of it is 166kg (this is just an example) is used for corner load test.
Variance should not be more than tolerance limit
Do not use the balance if variance is more than the tolerance limit.

Documentation: The calibration details should be properly documented, and calibration tracker should be used to track the next calibration due date.