Work
Instruction
Operation,
Calibration and Maintenance of Analytical balance (Sartorius)
(Analytical
Science)
Lab
Code
Version No.:
Effective
Date:
Review Date:
Supersedes:
Author(s):
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Technical Approver
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Authorized By
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Name
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Designation
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Signature
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Date
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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.
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S. No.
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Make
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Model
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Readability
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1
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Sartorius
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GP3202-OCE
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0.5g
– 3200g
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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.
2.4
Maintenance:
2.4.1 Cleaning
2.4.1.1 Remove
the weighing pan and weighing chamber plate.
2.4.1.2 Clean
the weighing chamber with a soft brush or a damp cloth.
2.4.1.3 Commercially
available cleaning agents may be used for cleaning the balance. Do not use
abrasive
cleaners or powerful solvents.
2.5 Servicing:
2.5.1.
Regular
servicing of the equipment is covered under annual maintenance contract which
ensures smooth functioning of the balances.
2.6
Special Instructions
Nil
2.7
Reference
Operating instructions, Sartorius AG
3.0
Appendices
Nil
4.0
Revision History
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WI No.
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Supersedes No. & Date
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Changes made (in brief)
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============================================================================
Work
Instruction
Operation,
Calibration and Maintenance of
Analytical
Balance
(Mettler)
(Analytical
Science)
Lab code…
Version No.:
Effective
Date:
Review Date:
Supersedes:
Author(s):
|
|
Technical Approver
|
Authorized By
|
|
|
Name
|
|
|
|
|
Designation
|
|
|
|
|
Signature
|
|
|
|
|
Date
|
|
|
|
1.
Scope
This work instruction
is applicable for the operation, calibration and maintenance of the following analytical
balances located in the Chemical & microbiology labs of Analytical Sciences.
|
S.
No
|
Make
|
Model
|
Range
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1
|
Mettler
Toledo
|
AG 245
|
0.01
mg to 41 g
0.1
mg to 210 g
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2
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Mettler
Toledo
|
AG 204
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0.1
mg to 210 g
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3
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Mettler
Toledo
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AB 304-S/FACT
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10
mg to 320 g
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2.
Procedure
2.1.
Operation:
2.1.1.
Ensure
levelling of the balance by turning the two levelling feet at the rear of the
balance housing until the air bubble is in the centre of the levelling control.
2.1.2.
Press
the << ON/OFF >> key to switch on the balance. When the normal
weight display appears, the balance is ready for weighing.
2.1.3.
Open
the right draft shield door in Mettler Toledo balance.
2.1.4.
Place
the container/ butter paper on the weighing pan and close the shield door.
(Ensure all the doors are closed prior to weighing each time to get accurate
weighing results)
2.1.5.
Press
<< → O/T ← >>key to tare the weight.
2.1.6.
When
the zero display appears the balance is ready for weighing
2.1.7.
Open
the draft shield, transfer the weighing sample on the pan and close the draft
shield
2.1.8.
Wait
until the circular symbol of the stability detector fades. When the symbol has
faded, the weighing result is stable
2.1.9.
Now
read off the displayed weight
2.1.10. Switching between weighing units
·
The
balance displays the result in weighing unit 1 (say g)
·
Press
the << F >> key briefly
·
The
balance displays the result in weighing unit 2 (say mg)
·
To
return to weighing unit 1, press the << F >> key again
2.1.11. To switch off the balance, press and hold the << ON/OFF >> key until the message
“OFF” appears in the display
2.1.12. After switching off, the balance will be in the
standby mode. For another weighing to be performed, place the weighing sample
on the pan and the balance will display the result immediately. (No need to
switch it on using the << ON/OFF >> key)
Note: It is advisable not to disconnect the instrument from the power supply
but to switch it off only by using the << ON/OFF >> key which
assures that the balance is always in thermal equilibrium.
2.1.13. Model AG-245 is a dual-range balance. This has a fine
(semi micro) range from 0 to 41 grams. In this fine range the balance shows the
result with a higher resolution, i.e. with one decimal place more. This fine
range cannot be moved, i.e. it always starts at 0 and ends always at 41
grams. The balance automatically
operates in the normal weighing range when first switched on. By briefly
pressing the «1/10d» key, you can switch to the fine range. The fine range
remains active up to a weight of 41 grams.
Note:
Below 41 grams, you
can switch between the fine range and the normal weighing range at any time by
pressing the «1/10d» key. If the weight is greater than 41 grams, the balance
quits the fine range and displays in the normal weighing range. If you remove
or decrease the weight following a weighing in the range above 41 grams, the
balance automatically returns to the fine range.
2.1.14. Refer to the manufacturer’s operating instructions for
further guidance on the operation of the controls of individual instruments.
2.1.15. Avoid the use of weighing vessels made from ferrous
metals on analytical balances, 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.
Note: Avoid the use of plastic vessels on analytical
balances in order to reduce the effects of
static electricity on the readings.
2.2.
Calibration
and Frequency:
2.2.1.
Balance
is calibrated internally (2 weights check every day) and externally by a
service engineer once in a year for the following parameters:
·
Linearity
·
Corner
Load Error
·
Measurement
Uncertainty
Note: Daily calibration is not necessary if balance is not used for the day
2.2.2
Record the internal calibration readings in the log as
per Appendix 1 and for external calibration ensure a calibration certificate is
provided along with the traceability documents.
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.
|
S.
No
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Make
|
Model
|
Range
|
Daily
Calibration check Weights
|
|
1
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Mettler
Toledo
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AG 245
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0.01
mg to 41 g
0.1
mg to 210 g
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10g & 31g
50g & 160g
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2
|
Mettler
Toledo
|
AG 204
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0.1
mg to 210 g
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50g & 160g
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3
|
Mettler
Toledo
|
AB 304-S/FACT
|
10
mg to 320 g
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80g & 240g
|
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.
|
Nominal Weight
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Allowable Range (g)
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Nominal Weight
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Allowable Range (g)
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1mg
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0.000999 - 0.001001
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50g
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49.95 -
50.05
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10mg
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0.00999 - 0.01001
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100g
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99.90 - 100.10
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100mg
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0.0999 - 0.1001
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160g
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159.84 - 160.16
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500mg
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0.4995 - 0.5005
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200g
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199.80 - 200.20
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1g
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0.999 - 1.001
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400g
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399.6 -
400.4
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10g
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9.99 - 10.01
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500g
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499.5 - 500.5
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20g
|
19.98 - 20.02
|
||
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 or Performance Check Failure
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.
2.4
Maintenance:
2.4.1 Cleaning
2.4.1.1 Remove the weighing pan and weighing chamber plate.
2.4.1.2 Clean the weighing chamber with a soft brush or a damp
cloth.
2.4.1.3 Commercially available cleaning agents may be used for
cleaning the balance. Do not use abrasive cleaners or powerful solvents.
2.4.2 Servicing:
2.4.2.1 Regular servicing of the equipment is covered under
annual maintenance contract which ensures smooth functioning of the balances.
3. Appendices
Appendix 1: Internal Calibration
Log for Linearity
Test in Analytical Balance (xxx)
