Analytical Balance Calibration (Updated)

CALIBRATION OF TOP PAN BALANCE

Calibration procedure

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 used. Note down the 10 measurements of the 10 mg weight in the performance check log. (Attachment no. 01) Variation in the observed weight from the mean value does not exceed ± 0.2 mg.

The 10 mg weight shall meet the performance check criteria of the mass value i.e. 0.1% of actual mass value. E.g. For all the 10 measurements of 10 mg weight, variation in the weighing cannot exceed 0.01mg.

Performance check

After the Auto calibration put 1 mg, 2 mg, 5 mg, 10 mg and 20 mg weights individually. The measurement shall be within the 0.1% of the actual mass value of the individual weight as given in the performance check log. (Attachment no. 02)

Measurement uncertainty check

The measurement of uncertainty shall be carried out by using 10 mg weight.
Put the external weight of 10 mg on the pan and note the 10 measurements. (Attachment no. 03)
Calculate the measurement of uncertainty as follows.
Measurement Uncertainity = Standard Deviation X 2
                                                     Actual Mass Value
Measurement of uncertainty shall be Not More Than 0.10.

Calibration frequency

It shall be performed daily, after any maintenance, after the relocation and after the power failure of the balance.

Each manufacturer supplies the maximum loading condition of the balance. The calibration of the balance shall be designed in such a way that the performance check weights cover the entire loading range of the balance. Lower and higher load limits shall be checked for the performance check. Before calibration make sure that the level bubble is in the center of the indicator and if internal calibration facility is available in the balance then it shall also be performed daily before performance check of the balance.

Always use a check weight appropriate for the particular balance. E.g. a 100 – mg check weight might be selected for a balance that has a load limit of 150 mg. Thus the operator must know the maximum capacity of the balance to select the correct check weight.

Attachment-1: Performance Check Log of Microbalance

Instrument:_____________________                                  Code No :______________

Make         :_____________________                                 Model   :_______________ 

Date	Level indicator check		1 mg	2 mg	5 mg	10 mg	20 mg	Weight box no. and valid upto	Done by	Checked by	Remark
Std. Wt. Cal No. Þ
Limit Þ		Bubble should be in Center	+ 0.1% of  Std. Weight (        to        )	+ 0.1% of  Std. Weight (        to        )	+ 0.1% of Std. Weight (        to        )	+ 0.1% of Std. Weight (        to        )	+ 0.1% of Std. Weight (        to        )

Attachment-2: Auto Performance Check Log of Microbalance

Instrument:_____________________                             Code No :______________

Make         :_____________________                             Model   :_______________ 

Check level indicator (Bubble should be in center) : _________________________________

                                                                  (Paste Performance check chart here)

       

Calibrated by : _______________                                               Date : ____________________

Checked  by : _______________                                                Date : ____________________

         

Attachment-3: Measurement Uncertainity Check of Microbalance

Instrument:_____________________                   Code No :______________

Make         :_____________________                   Model   :_______________ 

Date

Std. Wt.

Std. Wt. Cal. No.

Observation

of Uncertainty Less than or equal to 0.001

Weight box no. and valid upto

Done by

Checked  by

Remark

10 mg

Calculation
Measurement  =     Standard Deviation X 2  

uncertainty               Actual Mass Value