The basic components of the electronic belt scale mainly include: ⑴ belt conveyor and its drive unit (although the manufacturer of embedded belt scale generally does not provide it, the belt scale without it is incomplete and cannot work normally) ⑵ Weighing unit, ⑶ Speed measuring unit, ⑷ Signal acquisition, processing and control unit.
For conveyor belt scale, the whole belt conveyor is the carrier; For the weighing bench belt scale, its weighing platform, weighing idler and the section of conveyor belt just above it constitute a carrier.
Scale frame
1. Horizontal bar scale frame
There is only one group of weighing levers on which one or more groups of weighing idlers are supported. The weighing frame is usually composed of weighing levers, fulcrums, counterweights, etc. The structure is simple, but the weighing accuracy is not high, and the accuracy is usually 1%~2%.
2. Double lever scale frame
It is composed of two symmetrical groups of weighing levers. Each group of weighing levers supports one or more groups of weighing idlers. The scale frame has a complex structure and a large scale body. However, its two groups of weighing levers can offset the influence of some horizontal components (such as belt tension and side force caused by belt deviation) on the symmetrical weighing accuracy during the weighing process. Therefore, the scale frame has stable performance and high weighing accuracy, which is usually 0.25%~0.5%.
3. Cantilever scale frame
It is usually used on the special short belt conveyor. The whole of the short belt conveyor is only supported by the fulcrum and load cell. This scale frame is only used for the quantitative feeder with short size or the special metering belt scale. The weighing accuracy is medium, and the accuracy is usually about 1%.
4. Suspended scale frame
The suspended weighing frame is similar to the weighing platform for static weighing, on which one or more groups of weighing idlers are supported, and its characteristics are superior to those of other weighing frames of various structural forms mentioned above.
Weighing instrument
The weighing instrument has developed from the early analog instrument to the present microcomputer instrument. The instrument accuracy has developed from 0.1% and 0.05% to 0.01%. Microcomputer instruments are in the form of single chip microcomputer, PLC, industrial PC, embedded PC. The microcomputer type weighing instrument adopts the technologies of low drift high gain amplifier, high resolution A/D converter, flash memory, electrically erasable memory and non-volatile random access memory, RS - 232/RS - 485 communication standard, field bus, etc., which greatly improves its performance and functions. At the same time, it also applies Σ- Δ Modulated analog-to-digital converter and surface mounting of printed circuit board. The adoption of these new technologies has further improved the performance and reliability of weighing instruments and created favorable conditions for the miniaturization of instruments. In terms of performance, the nonlinearity is better than 0.01%, the sensitivity is better than 0.2 V/d, the A/D conversion speed is generally 10~30 times/s, and it can reach more than 100 times/s when used for dynamic weighing. Functions include: setting of various parameters, such as division value, range, calibration parameters, calculation coefficient, tare weight, etc; Zero point automatic tracking; Automatic peeling; Automatic range calibration; Dynamic detection; POST and fault diagnosis; Power failure data protection; Overload alarm; Nonlinear compensation; And the display of gross weight, net weight, tare weight and accumulated value. In order to facilitate communication with computers, current weighing instruments are equipped with input/output interfaces, such as RS - 232C, RS - 485, 20 mA current loop, analog quantity (4~20 mA) and relay output.