Weighing machines are highly simple machines ever known to man to be used in the history. The convenience of knowing the exact weight or to calculate the weight of the mass is popularly known as weighing machine. They were manually operated once upon a time. Even today manual method is in use in some of the parts of world. Especially they are used in rural parts. There are many types of weighing machines at present. In general, when anything is placed on the plate of the machine a force is exerted, and it is measured by placing equal weights on the other side of the plate, which is now replaced by the electronic display screens that automatically indicate the force or weight of the object placed on weighing platform. No doubt there is a huge demand for used weighing and bagging machines as they are available at cheaper rate than the new one in the market. Nowadays it is also very easy to get used cooking vessels.
Nobody cared for the weighing quality or precision until the industrial revolution took place. Scientists and people started paying attention only when they realized the importance of precision weights can play a decisive role in the results obtained in the experiments and results of variety of things. Then people in the industry started realized the necessity and need of precision weighing tools and techniques so that they can monitor even minute changes in the measurement. Once upon a time there were all chances of getting deceived in the reception of goods. Scientists and technicians realized that there is a need to develop standardized methods to measure and weigh things so that it will remain same across the globe.
Therefore, it has become all the more important to know the history and importance of standard system and principles lying behind the measurements. This has led to revolutionary changes in the system. Understanding the lever operations and applications of various techniques and the construction of scale become extremely important. It has become significant that the people should work in accordance with the rules and regulations set up by the weights and measurement department. These devices have become integral tools of commerce, without which it is impossible to carry out any regular business.
It is a long way from ancient scale, which is having a wooden beam that has two holes at either end of the beam and one at the center. This beam is supported by the center pole passing through the center hole. On the either side of the center pole there are two pans supported by cords. These pans also have equal weights. The first ever recorded weighing machine is Roman Steelyard. It allowed merchants to measure multiple weights easily and comfortably. It was constructed using a bronze beam and bronze weights allowing user to measure from 1 to 20 between its arms. The same principle is still used in the modern platform weighing machines as they provide accurate measurement; of course little changes are made as per the convenience.
Source : http://www.imfaceplate.com/machines4food/the-history-of-weighing-machines