History of weighing instruments

Weighing instrument is an important part of measuring instruments. In the past, people called measurement' weights and measures'. The so-called degree refers to measuring the length of an object with a ruler (such as ancient bone ruler, tooth ruler and bamboo ruler, wooden ruler, tape measure, steel ruler, etc.). ); The so-called quantity refers to measuring the volume of an object with containers (such as ancient closing, lifting, bucket, welcoming bucket and later measuring cups); The so-called scale refers to measuring the weight of an object. Balance should start from the end of primitive society. According to historical records, it has been more than 4000 years since. At that time, there was commodity exchange, but the measurement method was based on seeing and touching. As an instrument for measuring weight-weighing instrument, it first appeared in China Xia Dynasty. During the Spring and Autumn Period and the Warring States Period, I mastered the lever principle. In the mid-Warring States period and the mid-Chu period, scales and weights were widely used to weigh gold, but the measurement standards were different and confusing for a long time. It was not until Qin unified the world that the Shang Yang Reform was implemented in the 26th year of Qin Shihuang (22 1 year BC) that the measurement standards were unified. In Song Dynasty, a scale with the precision of 1 cm (40mg) appeared, which indicated that the weighing instruments at that time had a considerable technical level.

Weighing instruments are produced and developed in the process of commodity exchange. The earliest weighing instrument used by human beings was the original balance. About 5000 BC, Egypt used the equal arm balance (Figure 1). It sets a point in the middle of a simple lever, places the measured object on the disc (hook) at one end (right end in the figure) of the lever, and places the objects with the same shape and mass on the disc at the other end (left end in the figure) one by one. When the device is in a state of balance, it means that the masses of both sides are equal, and the mass of the measured object at the right end can be estimated by the number of objects at the left end.

The system of weights and measures in China began with the "Yellow Bell" law in 2500 BC. According to records, "the degree is based on the length of the yellow bell, the quantity is based on the relationship of the yellow bell, and the weight of the yellow bell is balanced." The yellow bell has been lost. In the Xia Dynasty, China began to use scales as weighing instruments. Strength is equal to weight, and balance refers to lever. There is a small hole in the middle of the lever as a fulcrum, and hooks are hung at both ends of the lever, and the weighed objects and weights are hung at the same time. Each trade-off has a set of weights. The weights on the right are increased one by one to weigh different weights. Wooden scales appeared in the Han Dynasty and have been used for more than 2000 years since then.

/kloc-in the 0/8th century, Scottish chemist J. Black first applied knives and tool holders to the balance, thus making accurate weighing instruments. 183 1 year, American T. fairbanks invented the platform scale, which integrated the advantages of unequal-arm bar scale and balance, and made various mechanical weighing instruments tend to be perfect. In the mid-20th century, a simple electronic weighing instrument appeared, which made the weighing instrument enter the electronic age. The combination of microprocessor and weighing sensor has caused the revolution in the field of weighing. Since then, the microprocessor has been widely used in weighing, especially in dynamic weighing, which basically replaced the original complex computing system. With the continuous development of microelectronics technology and the appearance of large-scale and ultra-large-scale integrated circuits, weighing and process control functions can be combined into the same electronic unit. In 1980s, electronic weighing instruments have spread all over the fields from micro-weighing to large-scale professional weighing, and the scales have developed to thousands of specifications, with the static accuracy generally above 0. 1% and the dynamic accuracy generally above 1% ~ 0.2%. There are about 250 weighing instrument factories in China, which can mass-produce large-scale special weighing instruments of 19 categories, 150 varieties and more than 500 specifications. The production of mechanical weighing instruments has reached a considerable scale, and the annual output of electronic weighing instruments has reached tens of thousands.

According to the structural principle, classified weighing instruments can be divided into three categories: mechanical scales, electronic scales and electromechanical combined scales. Mechanical scales can also be divided into lever scales (including equal-arm lever scales, namely narrow-sense scales and unequal-arm lever scales) and spring scales. Weighing instruments can also be divided into non-automatic weighing instruments and automatic weighing instruments according to measurement methods. The main types of weighing instruments are balance, pole scale, box scale, platform scale, floor scale, floor scale, track scale, loader scale, belt scale, postal scale, hanging scale, batching scale and bagging scale.