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Procedure for calibration of weighing balances
OBJECTIVE
To lay down a procedure for calibration of weighing balances.
SCOPE
The Standard Operating Procedure is applicable to In process Quality Assurance areas.
RESPONSIBILITY
Concerned Technician
ACCOUNTABILITY
In-process Quality Assurance Executive/ Officer.
PROCEDURE
DAILY CALIBRATION
Before calibrating the balance, clean the weighing platforms.
Take the standard weights of different capacity based on the capacity of the balance as mentioned in table – I.
Switch ‘ON’ the main power supply.
Wait till zero reading is displayed on the screen.
Allow to stabilize for 15 to 20 seconds and then select the weight for calibration.
Place the standard weight on the platform, the display should be same or within one least count., as per the weight placed.
Record the observations in balance calibration record format.
If the display is not matching to the weight placed and the difference is more than one least count than open the side pot and adjust with the screwdriver till it matches.
If the reading is not coming within one least count put an out of order label and get it rectified by the service engineer. Do not use the balance till it is rectified.
Note: Always use standard weights, which are certified by Weights and Measure Department.
TABLE – I
| S.NO. | CAPACITY | CAPACITY UTILISATION | WEIGHT FOR ACCURACY CHECK | LEAST COUNT | ||
| MAXIMUM | MINIMUM | MAXIMUM | MINIMUM | |||
| 1 | 1 Kg | 0.8 Kg | 20 gm | 0.2 gm | ||
| 2 | 35 Kg | 28 Kg | 500 gm | 5 gm | ||
| 3 | 60 Kg | 48 Kg | 1.0 kg | 12 kg | 10 gm | |
| 4 | 150 Kg | 120 Kg | 2.0 kg | 20 kg | 0.5 kg | 20 gm |
| 5 | 300 Kg | 240 Kg | 5.0 Kg | 50 kg | 1.25 kg | 50 gm |
| 6 | 600 Kg | 480 Kg | 10.0 Kg | 100 kg | 2.5 kg | 100 gm |
Figure – 1: LAYOUT OF PLATFORM
| a b
c
d e |
NOTE: a, b, c, d, and e are the locations as marked in figure – 1
MONTHLY CALIBRATION
Set the standard weights for various balances based on the capacity of the balance as mentioned in the table – I.
Before calibrating the balance, clean the weighing platforms.
Switch ON the balance.
Wait till zero reading is displayed on the screen.
Allow to stabilize for 15 to 20 seconds and then select the weight for calibration.
Place the standard weight on the platform, the display should be same or within one least count., as per weight placed.
Record the observations in balance calibration record format.
If the display is not matching to the weight placed and the difference is more than one least count than open the side pot and adjust with the screwdriver till it matches.
If the reading is not coming within one least count put an out of order label and get it rectified by the service engineer.
Do not use the balance till it is rectified.
Select the weight as given in Table -II for full range calibration as per capacity of the balance and observe the values.
Record the observations in format.
The balance is considered satisfactory if the error is found to be within one least count of the balance.
Check the zero repeatability by minimum standard weight and allowing to display correct value followed zero display on the removal of weight. Carry out the observation by putting weight on all four corners and at center.
TABLE – II
| S.NO. | CAPACITY | RANGE | |||
| 1 | 1 Kg | 0.2 kg | 0.4 kg | 0.6 kg | 0.8 kg |
| 2 | 35 Kg | 7.0 kg | 14.0 kg | 21.0 kg | 28.0 kg |
| 3 | 60 Kg | 12.0 kg | 24.0kg | 36.0 kg | 48.0 kg |
| 4 | 150 Kg | 30.0 kg | 60.0 kg | 90.0 kg | 120.0 kg |
| 5 | 300 Kg | 60.0 kg | 120.0 kg | 180.0 kg | 240.0 kg |
| 6 | 600 Kg | 120.0 kg | 240.0 kg | 360.0 kg | 480.0 kg |
Forms and Records (Annexures)
Not Applicable
Distribution
Master copy – Quality Assurance
Controlled copies- Quality Assurance, Production, Quality Control, engineering
History
| Date | Revision Number | Reason for Revision |
| – | 00 | New SOP |
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