New development of the hottest belt weigher Techno

2022-08-16
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New development of belt weigher technology

since its birth, belt weigher technology has been more than 100 years, and has experienced several stages, such as mechanical belt weigher, mechanical electronic belt weigher, electronic belt weigher, etc. after a hundred years of development, belt weigher has become increasingly mature and stable, and its application has become more and more widely. With the continuous emergence of new technologies, especially digital technology and networking technology, the technology of electronic belt weigher has also been developed. The following is a brief description of several development trends of electronic belt weighers:

1. Digitization of weighing signal

because the weighing sensor signal is only 0~30mv, it is not conducive to long-distance transmission, and it is also prone to interference. In order to enhance the anti-interference ability and meet the requirements of long-distance transmission in the tensile experiment of materials or small-diameter wire type materials, Seymour has developed a digital converter

the converter is installed next to the weighing bridge on site to convert the analog signal of the continuous weighing sensor into digital signal. Its circuit structure adopts 8-bit high-speed microprocessor and 24 bit AD converter, which effectively ensures the weighing accuracy of the system. The communication between the converter and the instrument adopts RS-485 serial communication, and the baud rates 9600, 19200, 115200 are adjustable. Due to the use of digital signal converter technology, the distance between the instrument and the weighing site can reach 2000 meters, which also greatly enhances the anti-interference ability of the system

2. Redundant design increases reliability

at present, belt weighers used for continuous weighing of materials on belt conveyors mostly use only one weighing sensor with only one weighing signal output installed at the position of one weighing sensor of the carrier as the measuring element, and a belt weigher weighing system is composed of one or more groups of such measuring elements, a speed sensor and an accumulator. The weighing sensor of the belt weigher with this structure has only one weighing signal output. When one of the weighing sensors fails, the whole belt weigher will not measure accurately, and it is not easy to find it during operation; This defect will cause unnecessary losses due to inaccurate measurement in the process of conveying materials

Seymour has developed a weighing control device of double bridge belt weigher according to the above situation. The device is composed of multiple groups of double signal output weighing sensor modules connected to the belt weigher carrier, two displacement sensors and accumulators; The accumulator includes a signal receiver connected to multiple groups of dual signal output weighing sensor modules. The signal receiver is connected to the processor, and the processor is also connected to displacement sensors and displays respectively. The working principle is shown in the following figure

the double bridge belt scale is composed of a weighing sensor with double bridge output. Because the output of the weighing sensor is two groups of independent weighing signals, during the process of conveying materials, the two groups of output signals are compared in real time through the instrument (Figure 1). When one of the two ways is abnormal, the accumulator will judge and display the normal cumulative quantity in time, the conveying work is not interrupted, and the system does not need to be shut down, Weighing data is still the sensor of the tensile testing machine: the accuracy and linearity of the sensor directly determine the accuracy and stability of the test data of the tensile testing machine for the yield strength of the welding strip, which can continue to be carried out reliably. There is no need to replace the weighing sensor, so as to avoid various losses caused by the need to calibrate the belt scale again due to the replacement of the weighing sensor. It solves the problem of inaccurate measurement caused by abnormal sensor in the transportation work, and it is not easy to find inaccurate measurement at the same time. The reliability and measurement accuracy of the belt scale are improved

Figure 1 Schematic diagram of weighing signal comparison

double bridge belt weigher adopts two displacement sensors, and the speed signals output by the two displacement sensors form two independent speed digital models through the shaper and enter the processor for signal processing. The software module speed comparator in the processor compares the above two speed digital signals respectively, removes the abnormal signals, and alarms them. It solves the problem of inaccurate measurement caused by abnormal displacement sensor in conveying work, and it is not easy to find inaccurate measurement at the same time

3. Real time calibration

Saimo Sanqiao series belt weigher is composed of three groups of independent weighing frames and a 6000 type weighing instrument controlled by 32-bit microprocessor. In the process of material operation, it realizes automatic calibration, comparison and zero adjustment, which greatly improves the reliability, stability and accuracy of weighing control of the belt weigher, and solves the problem that the belt weigher is not easy to calibrate in kind for many years. Its main working principle (Figure 2) is as follows

Figure 2 Schematic diagram of real-time calibration of belt scale

the measuring scale and gross weight scale installed on the belt conveyor adopt the method of mutual comparison to implement automatic calibration, that is, continuous material hanging calibration. First, the belt weigher compares and calibrates the measuring scale and the gross weight scale in the process of conveying materials, so that the two scales weigh the same amount of materials; Secondly, when the materials are normally transported, the standard weights are applied to the measuring scales. At this time, the two scales each get two sets of weighing values in the field of high-end new materials industry: the measuring scales with standard weights get the values of measuring the weight of materials and adding weights, and the gross weight scales only get the values of measuring the weight of materials. Since the two scales have been compared and calibrated in advance, the value of weighing and conveying materials is the same, and the weight value obtained by the weighing scale minus the weight value obtained by the gross weight scale is obtained. In this way, the standard weight value obtained by applying the standard weight can be detected by adding accessories according to the corresponding standard, so as to complete the automatic calibration

during the operation of the belt scale, materials are always stuck on the belt, especially when the conveying materials are wet. It is very difficult to automatically peel (zero) the scale, which affects the weighing accuracy of the belt scale. The tare scale installed behind the feeding port of the belt scale (there is no material in this area) only measures the tare value in the process of conveying materials by the belt conveyor. At the same time, the weighing scale obtains the measured material weight and the total tare value, and subtracts the value obtained by the weighing scale from the value obtained by the tare scale, so as to complete the real-time automatic zero and tare removal, which improves the weighing accuracy of the system

in order to make the weighing control more reliable when the belt scale is running, the weighing scale and the gross weight scale are compared in real time. If the deviation of the weighing values of the two scales is too large, the weighing instrument will automatically detect the output of the weighing sensors of the two scales. If the output of a sensor is abnormal, the scale using the sensor may have problems and give an alarm prompt in time. At this time, the system will use the scale with normal sensor output as the measuring scale, which increases the reliability of the belt scale

4. Networking

the networking of belt weighers is mainly composed of fieldbus and industrial instrument. At present, the popular industrial buses mainly include modbus, PROFIBUS DP, DeviceNet, can, etc. The development of industrial instrument has provided a machine for belt weighers to enter the Internet era. Putting belt weighers on the Internet for management will be the highest goal of its networking. Through the Internet, belt weighers can be calibrated and maintained anywhere in the world

in short, the development of the carrier (scale frame) of the belt scale has not changed much in recent years. The belt scale for trade uses multiple groups of weighing idler carriers, the belt scale for process control in the production process uses a single group of weighing idler carriers, and more uses the structure of direct pressure weighing sensors, which is a development trend. With the rapid development of sensor technology and electronic technology and the reduction of the cost of electronic components, belt weighers have benefited a lot. The adoption of advanced electronic technology and redundant design increase reliability; The adoption of real-time calibration technology has further improved the stability and accuracy of the belt weigher; With the adoption of new electronic technology, the performance and function of belt scale instruments have reached a new height

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