Work Instruction

Operation, Calibration and Maintenance of Analytical balance (Sartorius)

                                                         (Analytical Science) 

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1.     Scope

       This work instruction is applicable for the operation; calibration and maintenance of the following    

       Analytical balance located in Laboratory.

S. No.	Make	Model	Readability
1	Sartorius	GP3202-OCE	0.5g – 3200g

2.     Procedure

2.1       Operation:

2.1.1     Ensure leveling of the balance by turning the two leveling feet at the rear of the                        balance   housing until the air bubble is in the centre of the leveling control.

2.1.2       Press the “І/Φ” key to switch on the balance. When the normal weight display appears the balance is ready for weighing. Press the container / butter paper on the weighing pan.

2.1.3     Press “TARE” key to tare the weight.

2.1.4     When the zero display appears the balance is ready for weighing.

2.1.5     Transfer the weighing sample on the pan/container.

            key, If the symbol “          ” displayed during the operation, this indicates that the processor

            is performing a function and cannot receive further command at the moment.

2.1.7       Now read off the displayed weight.

2.1.8     Switching between the weighing units

 The balance displays the result in weighing unit 1 (say g)

•Press the “F” key for two seconds.

•The balance displays the result in weighing unit 2 (say kg)

•To return the weighing unit 1, press the “F” key again.

2.1.9     To switch off the balance, press and hold the “І/Φ” key until the message “OFF” appears in

             the display.

2.1.10    After switching off, the balance will be in standby mode. For another weighing to be perfomed, place the weighing sample on the pan and the balance will display the result immediately.

            Note:  it is advisable not to disconnect the instrument from the power supply but to switch it    

            off only by using the “І/Φ” key which assures that the balance is always in thermal equilibrium.

2.1.11    Refer to the manufacture’s manual for further guidance on the operation of the controls of individual instruments.

2.1.12    Avoid the use of weighing vessels made from ferrous metals on analytical balance, in order to reduce the effects of magnetic fields on the readings. For the same reason, magnetic stirrer bars must not be placed in vessels whilst weighing.

2.1.13    Avoid the use of plastic vessels on analytical balance in order to reduce the effects of static electricity on the readings.

2.2         Calibration and Frequency:

2.2.1     Balance is calibrated externally by a service engineer once in every 4 months for the

            following parameters.

·               Linearity

·               Corner Load Error

·               Measurement Uncertainty

2.2.2     For external calibration ensure a calibration certificate is provided along with the traceability

             certificates of the standards used in calibration.

            Note: All weights used in calibration must be traceable to national or international standards.

2.2.3     Linearity: Record the readings of two calibration weights. These should represent

            approximately 25% and 75% of the instrument’s capacity, where deviation from ideal linear

            behaviour is greatest.  In addition, full range calibration may be performed covering minimum

            to maximum of the   balance capacity.

2.2.4     Acceptance criteria: The readings must be within the tolerances determined for the certified   

            weights, e.g. those provided in the table below based on ±0.1% as per USP norms.

2.2.5       Corner Load Error: Place a weight equivalent to approximately 25% of the instrument’s capacity on the pan at the following locations: - Centre, Left Front, Left Rear, Right Rear, Right Front. Record the reading at each location.

2.2.6       Acceptance Criteria:  Each reading must meet the acceptance criteria stated under linearity.

2.2.7       Measurement Uncertainty: Place selected mass on the pan for 10 times and record the reading each time. Calculate the standard deviation (SD) for the 10 readings.

2.2.8       Calculate the minimum weight as (3  x  SD) / Nominal Weight

2.2.9       Acceptance criteria: <0.001g of the amount weighed

2.3        Calibration :

2.3.1     If any of the calibration tests are outside their specified tolerance, follow the

            procedure outlined below.

2.3.2       Determine if there is a reason for the failure. If a reason is found which can be corrected, make any necessary adjustments and repeat the tests.

2.3.3       If the tests pass, the original data is invalidated and the instrument can continue to be used.

2.3.4       If no reason for the failure can be determined, perform the tests twice. If both pass the instrument can continue to be used.

2.3.5       If any of the re-tests fail, identify the balance as defective and label it “Out of Service” and contact the service engineer to arrange a service visit.....



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