Operation and Calibration of Analytical Balance

1.0    OBJECTIVE:  

To lay down the procedure for Operation and Calibration of Analytical Balance.
  

2.0    SCOPE:

This SOP is applicable to the Operation and Calibration of Analytical Balance being used in Quality Control Laboratory.

3.0    RESPONSIBILITY: 

Microbiologist – To perform the operation as per SOP.

Head - Quality Control – To ensure the compliance of the SOP.

4.0    PROCEDURE: 

4.1    SWITCHING ‘ON’ AND ‘OFF’ OF ANALYTICAL BALANCE

4.1.1    Switch on the main power supply to AC power cord of AND  balance model No. GX-600 and keep as such for at least 1 Hrs to reach the required operation temperature. 

4.1.2    Press the ‘ON / OFF’ key [I/Q] from display panel to turn the display on.

4.1.3    After the balance is turned on, an automatic self test of the balance’s electronic circuit is performed and during this period O will be displayed in the upper left corner of the display panel.

4.1.4    At the end of the self test, a zero read out is displayed on display panel along with ‘g’ symbol on the display panel. 

4.1.5    Press the ‘REZERO key’ from display panel in cases where 0.0000 g is not displayed, wait till 0.0000 is displayed. Now the balance is ready for use.

4.1.6    After completion of weighing, press the on/off key [I/Q] from display panel to turn off the display  (stand by mode). During this period  ‘O’ will be displayed in the lower left corner of the display panel. 

4.1.7    Turn off the power supply to AC power cord.

4.1.8    If the balance is in ‘stand by mode’ press the on/off key [I/Q] on the display for operation and it does not require warm up.

4.2    Weighing of Samples :

4.2.1    Check the calibration status of the balance.

4.2.2    Check the spirit level of the balance.

4.2.3    Clean the outside doors, front side digital display position and inner pans carefully using tissue papers.

4.2.4    Switch on the balance as described in 4.1.1 to 4.1.5.

4.2.5    Weighing of the Solid Materials & Hygroscopic  Materials :

4.2.5.1    Open the upper door of the balance, place a polybag  on the balance.

4.2.5.2    Close the upper door of the balance completely and  tare the weight of polybag by pressing the RE-ZERO  key  after stabilizing the readout on display panel .

4.2.5.3    Adjust the weight of the sample quickly (if material is hygroscopic) by adding or removing material from the polybag  by means of a clean and dry spatula till the required weight is displayed.

4.2.5.4    Note down the reading after stabilizing the readout on display panel .

4.2.5.5    Close the door of the balance. Keep in stand by position or switch off the balance as described in the step 4.1.7 and 4.1.8.

4.3    CALIBRATING THE BALANCE 

4.3.1    Switch on the balance as described in the step No. 4.1.1 to 4.1.5.

4.3.2    Clean the outside doors, front side digital display position and inner pans carefully using a lint free cloth/tissue paper  that is moistened with warm water and a mild detergent.

4.3.3    Check the spirit level of the balance.

4.3.4    AUTOCALIBRATION  

4.3.4.1    Press the CAL key to start calibration.

4.3.4.2    The balance display displays CAL in and performs calibration.Prevent vibration and drafts from affecting  the balance.

4.3.4.3    At the end of  calibration balance shows CAL out and it automatically returns to the weighing mode after calibration.

4.3.5    External Calibration Programme with standard weights consists of the following :

4.3.6    Acceptance Criteria :

4.3.6.1    If the results are out of 0.1% of standard weight (200.0 g to 20g), call Service Engineer for rectification.

4.3.6.2    For uncertainty test the limit is not more than 0.001 for 200mg,1.0 g and 200.0 g.

4.3.6.3    The requalification of the balance shall be done every year by the  supplier or authorized supplier representative.

4.3.6.4    The balance shall be calibrated as per calibration programme given in 4.3.4 or whenever it is shifted or repaired

hichever is earlier.

4.4    PRECAUTIONS 

4.4.1    Keep the balance always clean.

4.4.2    Don’t allow highly corrosive materials to come into direct contact with the pan of the balance.

4.4.3    Clean the outside doors, front side digital display position and inner pans carefully using a lint free cloth/tissue paper  that is moistened with warm water and a mild detergent.

4.4.4    Spirit bubble should be at the center of the spirit level circle.

4.4.5    To deliver exact results, the balance must warm up for at least 1 hour after connection to AC power or after a power outage.

4.4.6    Keep the doors of the balance closed while recording the weight and whenever the balance is not in use. 

Analytical balance, microbiology,