Analytical balances are very sensitive pieces of instrument as well as may measure mass down to only 0.00001 gram. An analyst might require this sort of specificity with the substance she is weighing, so accurateness is vital. A calibration procedure assures the analyst that the balance is working accurately, but the calibration is only as fine as the analyst’s calibration technique.
Calibration is a very significant to the correctness of any balance. Just as a musician should have one true tone to tune his instrument, a balance needs a true weight to tune itself. Calibration is done by giving a base point (ZERO) as well as establishing what the filled capacity (SPAN) weight is. Since SPAN is usually the balance’s maximum capacity, the balance now has two precise great points: zero and full scale. The balance can now precisely calculate all amounts in between the base point (ZERO) as well as full capacity (SPAN.)
Balances are influenced by revolutionize in humidity, seasonal temperature, barometric pressure as well as the gravitational acceleration (the position of your place related to magnetic north) for the location at which the accuracy weighing instrument is being used. It is also recommended that a balance be calibrated frequently in order to obtain the most Precision Balances.
CALIBRATION OF TOP PAN BALANCE
Calibration process Internal calibration It shall be performed as per the manufacturer’s instructions. Drift check For the calculation of the drift 10 mg weight shall be utilized. You have to write down the 10 measurements of the 10 mg weight in the performance check log. Variation in the observed weight from the mean value does not go beyond ± 0.2 mg.
The 10 mg weight should fulfill the performance check criteria of the mass value i.e. 0.1% of actual mass value. E.g. For entire the ten measurements of 10 mg weight, variation in the weighing cannot exceed 0.01mg. Performance ensure After the Auto calibration put 1 mg, 2 mg, 5 mg, 10 mg as well as 20 mg weights individually. The measurement should be inside the 0.1% of the actual mass value of the individual weight.
Measurement uncertainty check The measurement of doubt shall be carried out by utilizing 10 mg weight. Put the external weight of 10 mg on the pan as well as note the 10 measurements. (Attachment no. 03) Calculate the measurement of uncertainty as follows.
Measurement Uncertainity = Standard Deviation X 2 divided by Actual Mass Value
Measurement of uncertainty should be Not More Than 0.10.
It shall be performed daily, after any maintenance, after the relocation as well as after the power failure of the balance. Calibration of the balance should be designed in such a way that the performance ensure weights cover the entire loading range of the balance. Lower as well as higher load limits should be ensured for the performance check. Before calibration make sure that the level bubble is in the center of the indicator as well as if internal calibration facility is available in the balance then it should also be performed every day before performance confirm of the Analytical Balances. Always utilize a check weight appropriate for the particular balance. E.g. a 100 – mg check weight might be opted for a balance that has a load limit of 150 mg. Thus the operator must recognize the maximum capacity of the balance to select the accurate check weight.