Weighing Balance

• Weighing is one of the most common tasks in the microbiology laboratory.
• Microbiology laboratory weighing balance mainly used for media preparation,micro pipette calibration and product testing purpose.
• Advanced micro,semi-micro,analytical and precision balances have now been perfected to such a degree that, in general, no special weighing rooms are needed.
• For more information refer USP general chapter 41 & 1035.

Weighing bench:

• Stable (lab bench,lab table,stone bench).
• Anti-magnetic (no steel plate).
• Protected against electrostatic charges (no plastic or glass).
• The weighing bench should be fixed either to the floor or on the wall. Mounting the bench on both places at once transfers vibrations from wall and floor.
• Reserved for the balance.

Work room:

• Vibration -free

Temperature:

• Keep the temperature of the room as constant as possible. Weighing results are influenced by temperature ( Typical drift: 1-2 ppm/°C).
• Do not weigh near radiators or windows.

Atmospheric humidity:

• Ideally, the relative humidity (% RH) should be between 45 % and 60%. B
• Balance should never be operated above or below the measuring range 20 to 80 % RH.

Light:

• If possible, place the balance on a window-free wall. Direct sunlight (heat) will influence the weighing results.
• Place the balance a significant distance from lighting fixtures to avoid heat radiation.This especially applies to light bulbs. Use fluorescent tubes.

Air:

• Do not place the balance in the air flow of air conditioners or devices with ventilators, such as computers or large laboratory devices.
• Place the balance a sufficient distance from radiators. In addition to the potential temperature drift, strong currents of air could interfere with operation of the balance.
• Do not place the balance next to a door.
• Avoid places with high traffic.

Operation of the Balance

• Do not disconnect the balance from the power supply and always leave it switched on. This allows the balance to reach thermal equilibrium.
• When allows the balance to reach thermal equilibrium.
• When you switch the balance off, use the display key (on older models the tare key). The balance is now in standby mode. The electronics are still energized and no warm-up period is necessary.
• We recommend a different warm-up time for each balance when it is first connect to the power supply. These are

1. Up to 12 hours for micro balances.
2. Approximately 6 hours for semi-micro and analytical balances.
3. Approximately 3 hours for precision balances.

Weighing vessel:

•  Use the smallest possible weighing vessel.
• Avoid weighing vessels made of plastic when atmospheric humidity is below 30-40 %.
• These conditions increase the risk of electrostatic charge.