Precision weighing refers to the process of measuring weight at a resolution of 1 gram or less with a high degree of repeatability. Precision, analytical and microbalances are designed to detect small changes in weight and must be sensitive enough to do so. It is their sensitivity that makes them susceptible to error caused by environmental influences. Just like many precision instruments, balances need to be used in an appropriate environment to ensure optimal results.

What Environmental Factors Affect Balances?

Because precision balances have such a high degree of accuracy, they are incredibly sensitive to external environmental conditions. Even minor disturbances can significantly impact your balance and cause measurement errors between measurements.

Temperature & Humidity

Inconsistent or incorrect temperatures and humidity cause condensation, static electricity, or expansion/contraction of materials which can substantially impact weight readings. Lab balances should be used in a controlled environment with consistent temperature and humidity. For most balances, the operating temperature range is between 40 and 100°F and a humidity of 40-60%. This will vary by manufacturer, so always check your user manual for proper environmental specifications.

Drafts & Air Movement

Air currents and drafts can come from vents, windows, fans, heavy foot traffic, or doorways. These air movements can disturb the weighing pan and cause instability on the display. Rapid, fluctuating readings often indicates air movement near and around the device. This is one of the most common causes of fluctuation we see at Scales Plus when troubleshooting with our customers.

Try to avoid rooms with drafts and uncontrolled airflow.  These may cause the movement of samples or negatively impact the scale’s reliability. If that is not an option, use a draftshield to avoid air movement interference.

Vibrations

Like air movement, vibrations will cause your balance to read improperly. Balances can pick up even small vibrations traveling through the floor from machinery in other areas within a facility. You'll notice the effect of vibrations on the balance by looking at the display. It will bounce between readings or fluctuate erratically. This is the second most common issue we see that affects weighing performance.

To eliminate or reduce vibrations, try to keep your weighing processes on the ground floor of your facility. If your company uses heavy machinery (e.g. hilos and stamping machines), make sure you are weighing in a room farthest from the area those machines are being used. The balance should be placed on a strong and stable work surface that is free standing. Specialty vibration dampening tables significantly reduce stability issues when using analytical balances.

Electrostatic Interference

A buildup of static charges can also adversely affect weight readings. This is more of a concern with high-precision weighing done with analytical and microbalances, but can impact any precision instruments.

The effect of static charges can be reduced by increasing the humidity in the room, using containers that are less prone to static (e.g. glass over plastic), or using external devices such as a static ionizer.

Power Instability

Unstable voltage (fluctuations or sudden changes in the power supply) can affect readings by interfering with the internal electronics of the balance. This electronic interference leads to inconsistent readings, an inability to zero, and/or erratic display behavior.

To avoid this issue, make sure your power supply (AC adapter) is in good condition and working properly. If you are using battery power, make sure the battery is charged each time you use the balance. If the battery will not charge, that is typically a good indication the battery is bad and needs to be replaced.

Geographical Location

Believe it or not, where you are located in the world matters! Depending on your geographical location, your balance’s performance could be influenced by local environmental and gravitational forces. To account for changes with gravity, your scale should be recalibrated when being moved to a different location.