The basic principle of multihead weigher and its rotary metrological verification technology

Author: Smartweigh–Multihead Weighter

The technical improvement of rotary metrological verification and its basic principle of weightless weighing 1. The current situation of the measurement verification method of rotary mixer 1.1 The rotary measurement verification method of traditional application has many methods in the measurement verification of fibrous raw materials such as decorative building materials, grain, oil, food, mining, etc., or when manipulating seasonings online . The more classic ones are: electronic belt scales, flushing plate flowmeters, nuclear scales, and disc feeding scales. This measurement verification method has its own characteristics, but the limitations are very large.

The processing technology of the electronic belt scale is introduced in detail. Steps: The electronic belt scale integrates the load data signal obtained on the total area (weighing section) of the enterprise and the data signal of the transition rate (transmission belt speed ratio) to obtain the total flow value. Manipulable targets. Note: The amount of material to be pulled out is changed according to the speed ratio of the drag-and-pull drive belt. After the raw material is shaped and beautified through the feeding port of the feeding chute, its thickness is stable and even. Regardless of the speed ratio of the belt conveyor, the load on the drive belt is fully is constant. Compared with other feeding methods, this method has a good actual effect of metrological verification and linearity.

1.2 Application of rotary metering verification method in continuous mixing machinery The current rotary mixing machinery includes: cement stabilized soil plant mixing machinery and equipment, concrete rotary mixing machinery, and bitumen rotary mixing machinery. As far as the precision of metrological verification is concerned, at this stage, this kind of equipment cannot be generalized with intermittent. Therefore, the rotary mixing method is not favored by many consumers, which is also one of the factors.

Scientific demonstration can show that the mixing and processing technology decided by these two measurement verification methods are all suitable places, and the application of rotary mixing should not be jeopardized because of the current technology limitations. At this stage, in our country, rotary mixing machines are all measured by volume method or electronic belt scale/spiral scale. In the 1970s, the continuous mixing processing technology was introduced from Europe to develop and design. So far, it has been like this, and there has been no improvement from beginning to end. In fact, these two measurement verification methods can be applied in Europe with high precision. For example, the transmission belt batching scale of Zhongshan Smart weigh has a dynamic seasoning accuracy of 2%.

But in my country, it is not good, because it depends on the restraint of basic industrial production such as machinery and equipment manufacturing and materials in my country. At this stage, the measurement verification accuracy of electronic belt scales used in the road field in China is generally only about 5%, which is no different from the capacity measurement verification, and the long-term reliability is weak. two. Continuous Weighing Reform——The multihead weigher (English Loss-in-weight) of the differential signal medicine reduction (weightless state) scale was first used in the whole process of industrial production in the 1990s for continuous metrological verification.

Multihead weigher gradually replaces electronic belt scales, spiral scales, and even accumulative scales. As a newest measurement method, more and more raw materials are gradually used. 2.1 Basic concept: Take the weighing bucket and the feeding organization as the whole scale body, continuously sample the net weight data signal of the scale body according to the instrument panel or the software of the upper computer, and measure the change ratio of the net weight in unit time as the instantaneous speed The total flow, and then through a variety of hardware and software filtering technical solutions, can be used as the other half of the adjustment“specific total flow”. The acquisition of this data flow is very critical, and it is the basis for the accurate measurement and verification of the weightless scale.

A traditional method is described in detail in the figure: the multihead weigher measurement verification method, and then the FC feeds back the optimization algorithm according to the PID opinion, carries out the operation calculation of the total flow close to the overall target, and outputs the adjustment data signal to operate the soft starter and other vibrating feeders. control panel. 2.2 The real application of the differential signal weighing scale (multihead weigher): From the working principle, it can be seen that it will not be affected by the mechanical equipment changes of the scale body and the feeding structure. It only measures the net weight error (difference weight), which is different from the traditional Compared with the dynamic metrological verification methods, its characteristics are obvious. When the control target is the total flow (t/h, kg/min), and the raw materials have good transportability, and the metrological verification precision standard is high, the weightless state method metrological verification can be used as a best plan.

2.2.2 The production process of weightless weighing: the production process of multihead weigher 2.2.3 Matters needing attention in the design scheme of weightless weighing, factors affecting the accuracy: multihead weigher has the characteristics of static data scale and dynamic scale. When formulating system software, it is stipulated that: 1. Appropriate transport rate range, generally in the specific work area, 60% to 70% of the rated transport capacity is the best. If the communication and exchange speed change is used, it is best to respond to the stress frequency of 35-40Hz. This ensures a wide range of adjustments.

It is also because when the transportation rate is too low, the stability of the system software is poor. 2. The measurement range of the sensor is moderate. In other words, the sensor also uses 60%~70% of its measurement range according to the formula. The data signal has a wide range of transformation, which is extremely beneficial to improve the precision. 3. The mechanical system design plan should ensure that the raw materials have good circulation, and also ensure that the pre-distribution time is short, and the feeding should not be excessively frequent. Generally, it takes 5-10 minutes to replenish the material.

The transmission device of the supporting facilities should ensure stable operation and good linear shape. 2.2.4 Application prospect: With the rapid development of electronic device control system, the multihead weigher is based on the selection of new technologies, and the accuracy of metrological verification is increased from 0.3% to 0.5%. And the increase to 0.1%~0.2%, or even beyond the static data scale, the key to this new process is the use of digital display weight sensors.

2.2.4.1 Application of digital display weighing sensor: In order to better integrate into the necessity of dynamic and accurate measurement, it is particularly important to be used as a system software key-in sensor in weighing equipment. Especially in the places that must be intelligent, the simultaneous or indirect data of the sensor is indispensable. At this time, the precise measurement uncertainty and detection rate are usually a pair of differences, and it is difficult to balance the two, and it is necessary to determine the specific situation. Make a compromise. In the weighing industry, many traditional digital analog sensors are basically manufactured and used in my country, and the output of the pulse signal is small.

Taking a weight sensor with a large total output and the basic principle of resistor strain force as an example, the general large output is 30-40mV. Therefore, the data signal is easily affected by radio frequency, and the transmission distance of the cable is also short, generally within ten meters. In the container weighing equipment (silo scale batching scale), service platform weighing equipment or scale bridge (electronic truck scale or rail scale) using several temperature sensors in series, the data operating system can be used to complete“self-calibration”.

This is due to the multi-channel digital sensor system software, there is no matching resistance problem. The customer can enter the detailed address, weighing and sensitivity of each controller, and then he can carry out the scale adjustment by himself.“four corners”or“edge”Balanced, no need to constantly adjust the letter again and again. In the system simulation, after several sensors are wired together, the characteristics of each controller will not be distinguishable from the others. When calibrating, the standard weight should be released on each sensor and the high voltage in the terminals should be used. The pressure regulator is adjusted.

Because there is a paired t-test when adjusting, it is repeated several times. In a data system, each sensor is allowed to be checked individually as a single. Therefore, the time to correct the total cost of the software with the digital sensor system is only 1/4 of the system simulation.

Using data system software can also be done“self-diagnosed”, that is, the diagnosis program flow continuously checks whether the data signal of each sensor is terminated, whether the output is significantly exceeded, etc. If there is a problem, a message or alarm is automatically displayed on the dashboard or control panel control panel, and customers can use the keys on the control panel to find each sensor, individually identify the cause of the problem and perform common troubleshooting. This type of judgmental diagnosis and problem clearing capability is clearly a key advantage to the customer, but it is difficult to forget and do it at low cost in the simulation of analog sensor system software.

In the weighing industry, the resolution of the displacement coefficient SPWM of the typical simulation sensor system software is 16 bits, and there are 50,000 available counts; and the screen resolution of each sensor in the data system is 20 bits. , there are 1,000,000 available counts. Therefore, a system software with 4 digital sensors can produce a screen resolution of 4,000,000 counts. The advantages of such high pixels are especially suitable for places where the weighing frame is very heavy and the net weight of the weighing object is small.

For example: in the seasoning weighing equipment, sometimes a certain type of raw material only accounts for a small proportion in the secret recipe, but the accuracy requirements are still very high. This is also impossible to achieve in traditional system simulation. three. The application of rotary mixing equipment and the impact of market prospects Because the measurement and verification of China's rotary mixing machinery remains in the traditional method, the application prospect of weightless weighing in marketing and promotion will be very broad. , The continuous mixing process of bitumen has subversive changes, and the accurate control of data flow can produce a very standard and ideal mixing material.

Because the rotary stirring process is simple in structure and low in maintenance costs, once the product mix ratio is strictly controlled, it will change the current situation of the low market share of rotary stirring. In particular, the production-increasing machinery and equipment required in the fields of road and hydropower engineering has positive significance, and weightless weighing is a key improvement to improve the measurement accuracy.

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