A scale is a device that, according to the dictionary of the Royal Spanish Academy ( RAE ), is used to measure weights . The term comes from the French word bascule .
Scales, therefore, are scales : artifacts that allow weighing. The action of weighing, in turn, refers to determining the mass or weight of a body .
In general, scales have a horizontal surface on which the elements to be weighed must be placed. Thanks to its structure, it is possible to know the weight of very heavy objects, something impossible with ancient instruments that required hanging the things that were intended to be weighed.
There are various types of scales. Broadly speaking, it is possible to differentiate between electronic scales and mechanical scales .
Electronic scales have load cells : sensors with metal parts attached to strain gauges that, when compressed, modify their electrical resistance and allow weight to be measured. These scales display the weight in question on a screen.
In the case of mechanical scales, nowadays they usually have an elastic spring . Previously, however, they worked with levers and measured weight indirectly through a counterweight .
It is important to note that, although they are used synonymously, there are differences between mass and weight . Mass refers to the amount of matter in a body and is expressed in grams , while weight reflects the action of the force of gravity on the body and is expressed in newtons . Depending on their characteristics, scales specifically measure mass or weight.
Bathroom scales are used in many homes. People who care about their physical appearance usually combine physical exercise with a balanced diet and, to control their weight, place a scale in the bathroom to keep an eye out for any irregularities.
On the other hand, there is the so-called weighbridge , a fundamental tool in measuring the weight of heavy vehicles, such as trucks, tractors, train cars, dump trucks and even aircraft . At first glance, it consists of a platform made of metal or concrete that is placed on top of interconnected load cells. The latter are linked to a sum box, from which the electrical signal is sent to a terminal where the weight of the object can be seen.
The most sophisticated weighbridge models also have access barriers, card readers, elements to correctly position the vehicle, traffic lights and devices to identify the license plate, among other features. Before use, they must go through a legal process of verification, sealing and approval by an authorized body. In Spain, for example, there are some public companies that depend on the Government that provide this service . Sometimes it can also be provided by certain private entities.
Among the technical features of a scale of this type, we can highlight the following:
* As expected, it must be capable of supporting a really considerable load, which can be counted in dozens of tons;
* The readings must give reliable results, since the weight of the vehicles is strongly linked to traffic regulations . For example, it is not possible to use a bridge or a highway with a truck of any weight, but there is a limit to avoid wear and tear;
* must have a work platform with sufficient width for different types of vehicles;
* One of the most important points is that the measurement should not be affected by meteorological phenomena, such as humidity, rain and atmospheric pressure.
In the military field, finally, a scale is a machine used to raise a drawbridge .