Purpose
This SOP describes the procedure for operation and calibration of Analytical Balance.
Procedure:
Operation
- Ensure that the balance is placed on Anti Vibration Table (
- Ensure that the balance is clean.
- Switch ON the main power supply of balance.
- Press the ON/OFF key of balance.
- Switch “ON” the Balance at least 30 minutes before operation for any weighing.
- Press TARE key to prevent possible error before placing material on the pan each time.
- Place a container or a piece of butter paper for weighing on the weighing pan.
- Press TARE to cancel net weight and TARE. The balance displays ZERO.
- Wait for the stabilization indicator to be displayed.
- Transfer the material to be weighed on the balance pan. Adjust appropriate quantity of sample. Wait for stabilize indication to be displayed & record the weight in respected documents.
- Whenever required, take the back weight of the paper or container.
- Clean the balance pan and surrounding using tissue paper.
- Operate the Balance as per procedure described in point 4.1 & 4.2.
- Verify the balance daily and external verification with external calibrated and certified weights. Calibration of weights should be traceable to national standards.
- Use the calibrated and certified weights.
- Screen will Display “0.000”,
- Use 1.000g, 5.000g and 10.000 g weights for daily verification of balance.
- Place the specific weight on pan with the help of a forceps. Wait until value is stable.
- Repeat the step for standardization sign appears all the other weights.
- Record the observations in “Daily verification record of analytical balance” The observed values of the weights should be within 0.1% of the weights.
- Calibrate the balance on monthly basis for the following.
- RSD determination for 0.500g, 1.0g, 10.0g and 100.0 g weights.
- Press TARE and check Display “0.000”, then place 0.500 g, calibrated weight on weighing pan with the help of forceps and wait until the reading is stable. Record the observation in “
- Take out the weight with the help of forcep from weighing pan and again place the same weight on the weighing pan with the help of forcep and wait until the reading is stable.
- Repeat this exercise for 10 times.
- Use 0.500g, 1.0g, 10.0g, and 100.0 g weights for monthly calibration of balance.
- Repeat the same step for all the other weights.
- Calculate the RSD of ten readings of all weights; it should be not more than 2.0 %.
- Record the observations in Monthly calibration record of analytical balance.
- Report any discrepancy observed during calibration of instrument to Quality Assurance In-Charge or his designee for corrective and preventive action.
- Quality Assurance In-Charge or his designee informs the defect to Engineering Department service engineer to rectify the defect. Affix ‘Under Maintenance’ label on the instrument
Determination of Mutual Uncertainity
- Press TARE and check Display “0.000”, then place 0.500 g, calibrated weight on weighing pan with the help of forceps and wait until the reading is stable. Record the observation in “Monthly calibration record of analytical balance”
- Take out the weight with the help of forcep from weighing pan and again place the same weight on the weighing pan with the help of forcep and wait until the reading is stable.
- Repeat this exercise for 10 times.
- After recording the weights of ten replicate calculate Standard Deviation in (Format No.
- Calculate the Mutual Uncertainity of ten readings of 0.500 g wt. Using this formula.
Certified Wt.
Eccentricity Check
- Use 10 g wt. for eccentric check
- Calculate the eccentric of 10 g wt. at different locations.
- Record the observation in
- Calculate the Eccentricity by using this formula
Actual Wt.
Precautions:
- Handle the instrument carefully.
- Do not load heavy weight, which is more than 80% of its capacity.
- The instrument should not be exposed near vibration forming devices.
- Ensure that the platform of Balance is anti-vibration table.
