Lever weighing 0.1 mg, the pinnacle of precision mechanical technology TG328A electro-optical analysis balance disassembled!

2015-05-18 12:00

Lever weighing 0.1mg, the pinnacle of precision mechanical technology TG328A electro-optical analysis balance disassembled! 【 Essence 】(1)


The typical development of leverage in China is the invention of the scale and its wide application. A lever is mounted on a rope as a fulcrum, one end of which hangs a weight, the other end hangs a weight or a scale, you can weigh the weight of the object. The ancient people called it "weighing" or "weighing instrument". "Power" is a weight or a scale, and "heng" is a scale. "Lu's Spring and Autumn Ancient Music" records that the Yellow emperor asked Linglun to "weigh and measure." "Shi Ji Xia Benji" records that Xia Yu "as a degree, called out." It is possible that China had a prototype weighing instrument as early as 4,000 years ago. However, the earliest scales excavated so far are those found in a Chu tomb on Zuojiagong Mountain near Changsha (Diagram 1). It's from the fourth or third century B.C. It's an equal-arm scale. The unequal arm scale may have originated in the Spring and Autumn Period (FIG. 2). The ancient Chinese also invented a scale with two fulcrum points, commonly known as the Baht scale (Diagram 3). With this scale, the fulcrum can be changed without the need to change the beam to weigh heavier objects. This is one of the major inventions of the Chinese in weighing instruments, and also shows that the Chinese fully mastered the principle of Archimedes (287-212 BC) lever in practice. (Partly quoted from ancient Chinese physics)



I. Appearance of electro-optical balance

Disassembled is a domestic automatic plus code electro-optical analysis balance, model TG328A, Xiangyi Balance instrument Factory in March 1987 production. The balance adopts equal arm lever structure, and has an air damping device, so that the stop point is fast, accurate reading, was once the industrial and mining enterprises, scientific research institutions, colleges and universities, laboratories, laboratories for precision weighing, analysis, determination of the ideal instrument.

Technical parameters:

Weighing range: 0 ~ 200g

Index value: 0.1mg

Optical reading range: 0-10mg

Mechanical code range: 0.01-199.99g

Pan size: Φ75mm

Size: 420mm×370mm×500mm

Net weight: 18kg







Back of the balance:





2. Mechanical structure


The structure of the electro-optical analysis balance is shown in the following figure: it is composed of a beam, a column, a suspension system, a reading system, an operating system and a balance box.

In order to prevent the erosion of harmful gases and dust and the impact of air flow on the weighing, the balance is placed in a three-way frame cover with glass doors (that is, the balance box), when taking and placing the weighed object or weight, the side door should be opened, and the main door of the balance is only used in regulation and maintenance. In order to increase stability, the base is made of white marble, and the whole machine is very heavy.



The operating system of the balance in addition to the mechanical loading device has a lifting pivot, which is installed in the middle of the balance, connected to the bracket, tray bracket and light source. Controlled by a lift knob. When the lifting pivot is opened, the joist is lowered, and the three knife edges on the beam contact the corresponding agate knife bearing (plate), and the tray support is lowered. The lifting lug and the balance plate swing freely, the balance enters the working state, and the light source is also connected, and the projection of the scale is seen on the screen. When the weighing is stopped, the lifting pivot is closed, then the balance beam and the pan are supported, the knife edge is separated from the agate plate, the balance enters the resting state, and the light source is cut off. The light screen turns black.

In addition, each balance comes with a box of matching weights. In order to facilitate weighing, the size of the weights has a certain combination form - usually in 5,2,2,1 combination, and in a fixed order on the weight tray.

Three, mechanical parts


Open the main door of the balance, with a self-locking mechanism, you can stop at any position:



Main door cable box with self-locking:





After opening the main door, the balance is in full view:



Beam, also known as balance beam, is the main component of the balance, generally made of copper or aluminum alloy. There are three prismatic agate knives on the beam. The middle one knife edge downward, called the fulcrum knife; There is a knife edge up at each end of the equal distance, called the load-bearing knife, the sharpness of the three knife edges determines the sensitivity of the balance, so great attention should be paid to protecting the knife edge. There is a balance screw (balance thallium) on each side of the beam for adjusting the zero point of the balance:

Ring weight of the balance (gram) :



Ring weight of the balance (mg grade) :





The optical reading system of the balance: as long as the lifting knob is turned on, the balance is in the working state, and the small bulb (electric bead) in the lamp holder behind the balance is lit, and the light is collimated. The scale of the microscale is projected on the projection screen, and the weight of 0.lmg to 10mg can be read from the projection screen.





Key words: lever weighing 0.1 mg precision machinery technology peak





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