Mass measurements are carried out worldwide at all areas, from the kilogram of potatoes to the ounce of gold to the ton of nitrogen, and each measurement gets carried out with appropriate precision. Metrology services and local calibration authorities ensure that the weighing is linked to the International Prototype Kilogram. This traceability chain guarantees that, for example, one kilogram in Sydney is identical to the kilogram in Shanghai, Sevilla or San Diego and ensures that transactions can be carried out uniformly across all borders. So far so good but ensuring the right unit of mass does not ensure the right measuring result.
Gravity is the force that pulls objects to Earth. It is often assumed to be the same everywhere on our planet, but it varies because the planet is not perfectly spherical or evenly dense. In addition, gravity at the equator is weaker due to centrifugal forces. The same applies to places that are at a greater distance from the center of the Earth.
Mass, a physical quantity, is a measure of the amount of material in an object. The unit of measure for mass is the kilogram (kg). Mass describes the property of an object. This property is revealed not only in the inertia of an object in changing its momentum (acceleration or deceleration), but also in the force of attraction between two objects. Thus, in the earth‘s field of gravity, each object is subject to a force.
W = m · g
m = mass
g = local gravitational acceleration
The force „W“ is commonly referred to as weight. Because gravitational acceleration depends on the particular location, weight also depends on location, whereas mass is independent of a location. For instance, if an object is transported to the moon – with its lower field of gravity – the mass of this object remains constant even though its weight changes.
Force is not mass
Force, or weight, on the one hand, and mass, on the other hand, must not be confused: Force is the effect on an object that deforms or accelerates it (e.g., during free fall). Mass is a property of an object, describing its quantity.
There is an additional difference between force and mass: To describe a force, its size and its direction of action must be defined. This is unlike mass, where defining its size suffices. The units of measure for mass and force are likewise different. Mass is measured in kg, whereas force is measured in Newton (abbreviated „N“), where 1 N = 1 kg · m/s².
Weighing instruments are designed for measuring mass
Advanced electronic scales determine the mass of an object by the effect that the gravity of Earth has on this object; i.e. they measure the weight “W” according to equation above. However the read-out is converted to the mass unit kg.
Because the gravitational acceleration “g” depends on the particular location, the sensitivity of electronic scales must be re-adjusted each time they are moved to a different location. For instance the gravitational acceleration at the equator is about 0.5% less than that at the earth’s poles.
On the way to true value, there are many factors that can affect the outcome and anyone who is professionally involved in weighing should know the most important ones. The journey starts with the right weighing equipment, the right installation and calibration and ends with external factors like wind or heat.
Generally, the industrial weighing scale, a measuring instrument, is integrated into the production process at a specific point where it is intended to fulfil a certain purpose. The primary use of a scale is to weigh things. For this purpose, an appropriate vessel or a moveable container is placed or driven onto the scale, the scale is tared, and the solid or liquid sample is placed into the vessel or container according to the specifications. The weight is recorded manually or electronically and the sample, along with the container, is removed from the weighing pan on the scale.
Industrial scales contribute heavily to the process chain. In view of the wide range of scales, it is important to find a tailored solution for highly technological processes that seamlessly integrates into the existing production process. Seeking this solution involves both requirements on the equipment, such as the weighing range, the resolution or the repeatability of results, and also the physical characteristics, such as the material constituting the build of the scale. External factors such as outside interference or process requirements also place additional requirements on an industrial scale. So that the scale can communicate continuously with the other equipment, selecting the appropriate interface is also essential.
A counting scale can be used to rapidly and easily count any number of capsules and tablets, pellets, small parts or any other number of objects with the same weight and determine the total quantity. This requires placing a small known quantity of pieces on the counting scale. The scale calculates the average weight of the known number of pieces (for example 10 units) and stores this number in its memory. Later, this known average weight is used to instantly count unknown quantities of the same material regardless of how many pieces are placed on the scale. The results can be stored or printed out for record-keeping or for other documents that accompany the product.
The scale best suited for weighing moving items on a conveyer belt in a production line is an automatic checkweigher. This type of scale is particularly important in situations, where the need for clock speed or the requirement for 100% inspection prohibits manual weighing. The weight of each item on the conveyer belt is instantly compared with previously established product-specific limit values. Any item outside these tolerances is automatically removed from the belt.
This type of scale can also be used for classifying items based on pre-programmed user defined criteria. Since each unit is checked, any packages that are over - or under - filled can be identified and rejected quickly. Even the filling process can be controlled centrally. For process optimization, short and long term production performance can also be measured. Routine checkweighing procedures can be integrated seamlessly into simple or complex Statistical Process Control (SPC) systems. These, in turn, can be used to effortlessly carry out data analysis or for adjusting the filling heads in real time.
Minebea Intec Bench & Floor Scales
Batch weighing scales (for batching processes) are designed with scales or load cells, pipes, valves, electrical hardware and the process control software in an integrated control system. This kind of system controls one or several feed systems which convey the various user-defined quantities of raw materials in a common receiving vessel where the contents are mixed or made to react. As a rule, the receiving vessel is tared every time a new component is added. The system can also be set up to measure the weight loss in the individual ingredient vessels. Batch weighing scales are supplied in manual or automatic versions. Some batch weighing scales can also control other parameters involved in the processes taking place within the vessel like heating, cooling and mixing. And these are just a few of the scale’s potential applications.
Selecting the perfect industrial weighing scale provides several advantages for the user, such as:
Increased efficiency
Intuitive operation prevents errors in use
Minimising rejects
Reliable sample weighing
Saving time and cost when cleaning thanks to the hygienic design
Areas of application of an industrial weighing scale
Industrial weighing scales can be integrated at almost any point in the production process in various industries such as: food and beverages, pharmaceutical, chemical, electronics, logistics, agribusiness, cosmetics, building materials, recycling. Amongst others, the areas of application of an industrial scale are:
Check weighing and integrity checking
Classification, sorting and counting according to weight
Batching and formulation in recipe management
Checking ingredients, production quantities or goods issue
Order picking for shipping
Statistical control of production processes
