Weighing is a vital process that must be done properly for accurate results. Many factors can affect weighing including the operating surroundings, the sensitivity of the balance and the sample to be weighed.
For example, the air temperature of the weighing area should be the same as the temperature of the sample to prevent air currents that can affect the results. Good laboratory practices and standards are also important.
Accuracy
Accurate weight measurement is essential for industrial operations to ensure that processes are optimised, efficient and compliant with safety standards. It helps reduce waste by ensuring that raw materials are used effectively, minimising the likelihood of overproduction and cutting costs associated with costly corrections or reworks.
For accurate weighing, the balance should be properly calibrated and the environment should be well ventilated to avoid air currents. It is also important to select the right sensitivity weight for the application and use it correctly to minimise errors.
The accuracy of the weighing process depends on several factors, including balance drift, calibration, temperature variations, magnetic and electrostatic fields, sample characteristics (evaporation, hygroscopic/hydrophobic solid materials gaining or losing moisture) and manipulative skills during weighing. By working with reputable scale suppliers, utilising modern technology and implementing effective maintenance practices, organisations can maximise the benefits of an accurate weighing system. For example, accurate measurements ensure that ingredients are added in the correct sequence and proportion to maintain product quality.
Efficiency
Weighing operations are executed by using a variety of equipment including proper containers, receiving vessels, forceps, pipets and spatulas. If a quantity is too large for direct weighing, counting by weighing may be employed. In this case, the operator subtracts a certain amount from a full container until the desired reading is achieved on the balance pan.
In food production applications, accurate weighing is critical to ensure that all ingredients are distributed evenly and the end product looks and tastes the same each time. Garber offers a wide array of process weighing solutions including loss in weight controllers that connect to your enterprise resource planning system and help you understand the loss in weight of ingredients as they are weighed in your hoppers.
When performing direct weighing, a substance ought to be added directly into a tared container which will hold it rather than placed on the balance pan itself. This prevents air currents from affecting the weighing results. It is also important to exercise the balance before taking a reading.
Safety
Weighing systems can contain heavy components that must be handled safely. Keeping an eye on the area where they are located and ensuring that all individuals working on them wear proper PPE (personal protective equipment) helps to prevent accidental injury.
Environmental considerations must also be taken into account, particularly when working with hazardous chemicals. Fume hoods and safety cabinets help to keep dangerous substances contained, while gloves and appropriate ventilation systems can minimize any exposure. It is also important to use a device that can eliminate electrostatic charge from fine powders, as this can cause erroneous readings on precision balances.
Another technique that can help reduce error is weighing by difference. This involves weighing the container with its contents and then subtracting the weight of the substance that is to be removed from the total. The process can eliminate errors caused by initial readings on a balance as any mistakes are cancelled out when subtraction is performed.
Maintenance
Observing strict laboratory rules will help minimize errors in the weighing process. For example, a balance should not be touched with bare hands. Moisture, grease and dirt on the fingertips can affect the weight reading. Handling large objects or containers is also problematic, especially with lower tolerance classes. In these cases, special hoists and crane hydraulics are available to safely set the weight on the balance.
In order to prevent balance drift, it is recommended that the balance be calibrated on a regular basis using a check-weight of known mass at the current ambient temperature. Some electronic analytical balances require a “tare” button to be pressed before each weighing.
It is also helpful to test the weighing system with the actual material it will handle during normal operation. This will simulate handling dynamics and give a more realistic picture of its performance. This information can be used to make adjustments and improvements in the weighing system’s calibration.