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Everybody uses a weighing scale to check their body weight. Individuals use a bathroom scale to check body weight. Shopkeepers and food retailers use digital scales to weigh the food items they sell to their customers. Businesses and industries use them for weighing products and packages in warehouses.
But have you ever wondered how these weighing scales work? The working of these scales depends on the type of scale and the capacity for which they are made. However, the basic working principle is the same as they all measure the weight of the object placed on them. Let us dive deep into the working of weighing scales and know more about them.
A weighing scale has multiple components, but the main components are springs and load cells. Both the mechanical and digital scales work on the same principle except the way they display the results. A digital scale has a converter that converts the analog signal to a digital one that is displayed on an LCD display. Digital scales are easy to use for beginners who don’t know how to use or calibrate a mechanical scale.
Weighing Principle
The weighing cells working method is based on the Electromagnetic Force Restoration (EMFR) principle. The basic principle is very comparable to a single beam scale. The result is that the coil is attached to the other side and tries to get out of the magnetic field of the object.
On the scale, the photoelectric beam recognizes the minimum deviation. This amount of current is sent through the circuit or coil of the electric regulator. The balance beam barely moves and remains in its neutral position.
The deviation that occurs is only a few nanometers. The deviation that occurs is only a matter of a few nanometers. Also, there are movement-dependent measurement processes, such as with a strain gauge. The force applied to the system by the weight of the object is offset by the current passing through the coil.
The current is directly proportional to the force. It is measured with a measuring resistor. It is transformed into a digital signal by an analog-to-digital converter. It is further processed in a single processing system.
Load Cells
Although weighing scales are available in various sizes, types, and designs, load cells are the primary components that actually measure the weight of objects. Load cells are like a transducer that functions by converting the pressure applied into an electrical signal.
Working of load cell
When an item is placed on the weighing scale, its weight is uniformly distributed. There are four slightly raised pegs under the tray on which the object is placed. The function of these pegs is to distribute the force of weight uniformly, and this force is applied on one end of the load cell. This force comes from the weight of the object, and when it is applied on an end of the load cell, that end bends downward, and it converts the force into an electrical signal.
Strain Gauge
Some scales have a strain gauge that is another widely used component in weighing machines. Many industries require a strain gauge for their weighing equipment. A strain gauge is also a type of load cell. Digital scales use a strain gauge type of load cell, while analog instruments make use of springs to measure the weight.
A strain gauge measures the strain imposed by the object placed on the weighing machine, and the load cell converts the force into an electrical signal.
There are two types of strain gauges – hydraulic and pneumatic. Both are used in weighing instruments depending on the type of environment where they are required to be used.
Pneumatic load cells are used in food processing industries, while a hydraulic type is used in locations where there is no facility for electricity.
How does a strain gauge work?
Similar to the bending of the load cell, a strain gauge works by deforming itself in proportion to the force applied by the weight of an object that needs to be measured. Some types of strain gauges contain metal tracks, and some contain a foil that is bonded to a backing or printed circuit board. When an object is placed on the weighing scale, the backing is stretched, or the metal foil gets strained and produces an electrical signal in proportion to the stretch or strain.
Conversion to an electrical signal
Whether a weighing scale contains a load cell or a strain gauge, both of them convert the force of weight into an electrical signal. Let us know how they do it and measure the weight of an object.
As mentioned above, a strain gauge is deformed due to the pressure or force applied by the weight of the object. This deformation of the strain gauge produced an electrical signal that is proportional to the amount of deformation.
In the case of a load cell, it has an electric charge. As one end of the load cell moves downward, its resistance changes, and this resistance itself becomes an electrical signal that is proportional to the bending on the load cell end.
In the case of analog scales, this electrical signal produced is sent to the analog display to enable the user to read the result. However, the process is different in the case of digital scale. In the case of digital scales, the electrical signal is sent to an analog to digital converter, which converts it into a digital signal. This signal is sent to a microchip that produces the final data in the form of digits that are then displayed on a liquid crystal display (LCD) or LED display.
Final Words
These were the working principle and mechanisms of weighing scales. Some industries prefer scales equipped with a strain gauge, while others prefer scales with load cells. The type of scale an individual or business chooses depends on their requirements. For example, a weighing scale used by a grocery store is different than the one used by a warehouse. However, the basic working principle of all the weighing scales is the same, that is, to measure the force exerted by the weight of an object and display the result in the units of weight.
