OPERATION AND CALIBRATION OF PRECISION STANDARD ELECTRONIC BALANCE (OHAUS)

1.0 OBJECTIVE
To ensure that instrument performs satisfactorily and gives accurate and reproducible results.
2.0 SCOPE
This sop is applicable to the Quality Control Department.
3.0 RESPONSIBILITY
Quality Control Chemist/Executives
4.0 ACCOUNTABILITY
Department Head.
5.0 GENERAL CLEANING PROCEDURE
5.1 Daily clean the external surface of the balance with dry mop immediately after use.
5.2 Once in a month clean the external surface with a wet mop dipped in 2.5 % savlon solution and ensure that no water goes into the balance while cleaning.
6.0 PROCEDURE :
6.1 Place the balance in a place which is free from excessive air currents, vibration and temperature extremes.
6.2 Keep the balance on a leveled work surface.
6.3 Make sure the hole in the pan support faces the rear of the balance and place the pan on the support making sure that the guide pin is inserted in the hole in the pan support.
6.4 Plug the molded connector of the adopter into the receptacle at the rear of the balance and plug the adopter into power socket.
6.5 Turn the balance ‘ON’ when no load is on the pan ,by pressing the ON TARE button.
6.6 After the display check is over , the display will momentarily be blank and then indicate ‘* 0.00g’.
6.7 Weigh the sample as follows :
ON TARE
6. 7.1 Place a clean butter paper on the platter, and depress the "ON TARE" button twice.
6.7. 2 The weight window shows 0.00 kg.(If you remove the butter paper, the display reads the tare weight of the paper)
6.7.3 Transfer the substance to be weighed carefully on to the butter paper as required. Note the weight.
6.7. 4 Transfer the substance to the required container and place the butter paper on the pan. The balance displays any weight remained on the paper. Note the weight. Calculate the actual weight transferred.
7.0 Calibration against standard weights
7.1 Ensure that the power supply to the balance is switched ‘ OFF’ before cleaning
7.2 Clean the pan with a clean dry cloth.
7.3 Check that the air bubble is in the center of the level and of necessary adjust the level by turning the leveling screws and close the balance doors.
7.4 Switch on the balance and allow it to stabilize for 30 minutes.
7.5 Check the weight of the following standard weights 100 gm, 200 gm, 2000 gm.
7.6 Record all the results in the format as per annexure-I
7.7 ACCEPTANCE CRITRIA
For 100 gm ± 0.5 gm,
For 200 gm ± 0.5 gm,
For 2000 gm ± 2 gm.
7.8 Report for any discrepancy noted at the time of calibration or operating the instrument to Department Head and notify the defect to the technical officer for rectifying the instrument. Affix a “BREAKDOWN LABEL” to the balance and discontinue the use till the balance is rectified.