Weightless weighing: the principle and calculation method of multihead weigher

Author: Smartweigh–Multihead Weighter

In this paper, the principle and metrological verification method of multihead weigher are introduced in detail from the aspects of composition and structure. The multihead weigher is a continuous feeding machine with the function of metrological verification. It is designed based on the basic principle of controlling net weight damage during work, and is widely used in automatic batching systems in production. Keywords: multihead weigher basic principle of metrological verification In the carbon forming process of the enterprise, the automatic batching system is a very critical operation and metrological verification system software, which is very harmful to the quality and index value of carbon anodizing production. It consists of a multihead weigher and 4 electronic belt scales (introduce the name).

Based on the hard study, practical activities and scientific research of the three multihead weighers, the editor has some superficial understanding and understanding of the multihead weigher. Here, the key is to carry out a simple and detailed introduction to the basic principles and calculation methods of the multihead weigher. Share it with the guys. 1. Structural composition The multihead weigher is generally composed of key parts such as the feeding water conservancy gate, the weighing silo, the stirring device, the feeding equipment, the sound card frame, the weight sensor and the measurement verification control equipment. 1. Feeding water conservancy gate The feeding water conservancy gate is used to feed the weighing hopper. Gate valves, butterfly valves, gate valves, etc. are mostly used. Generally, the key concerns are its sealing, power switch coordination ability, and rapid and smooth feeding. performance parameters.

2. Weighing silo The weighing silo is the medium for weighing raw materials. The selection of raw materials should take into account corrosion resistance and alkali resistance. The proportion of the whole weighing process should be about 10%. 3. Stirring device The stirring device is mainly used to assist the pouring of raw materials with poor circulation. It is generally composed of a simple drive motor of an arch-breaking arm machine with a spiral auger blade or a spike. According to the rotation of the arch-breaking arm, it is easy to appear. Raw materials for arching and rat holes can be dropped smoothly into the entry and exit locations. 1 Feeding water conservancy gate 2． Weighing hopper 3. Weight sensor 4 sound card rack 5. Mixing device 6 Feeding equipment 4. Feeding equipment The feeding equipment is used to discharge the fibrous raw materials in the weighing hopper. According to the characteristics of the raw materials to be transported and the application natural environment, screw conveyors, impeller feeders, Feeder, belt feeder.

In most applications, the screw conveyor is better than other closed feeding equipment. It can not only transport raw materials evenly, but also avoid the flying and gushing of powdered raw materials. 5. Sound card rack The sound card rack is the support point of other machines and equipment, and the weight sensor is installed on it. 6. Weight sensor The weight sensor is the key weighing component of the multihead weigher, and a solid high-resolution resistance strain gauge sensor is mostly used, which converts the net weight data signal of the raw material into an electronic signal for output.

7. Metrological verification control equipment Metrological verification control equipment is composed of a fully intelligent multihead weigher dial and a fully automatic automatic control system, which is used to carry out control and metrological verification of feeding speed, transportation capacity, etc. In addition, the inlet and feed ports of the multihead weigher should generally use soft anti-fouling and airtight conductive soft connections to ensure that the connection between the storage hopper and the subsequent equipment does not hinder the weighing. The weighing silo of the multihead weigher and the adjustable feeding device installed under it are located on the weight sensor fixed to the sound card rack.

2. Principle 1. Principle As shown in the figure, the multihead weigher completes the metrological verification according to the basic principle of manipulating the net weight damage during work. First, weigh the feeding equipment and the weighing silo, compare the specific feeding speed with the set feeding speed according to the damage of the net weight per unit time, and then control the feeding equipment to make the specific feeding speed accurately meet the preset value from beginning to end. , In the whole process of feeding in a short period of time, the feeding equipment relies on the force to make the manipulation data signals stored in the middle of the work work according to the basic principle of capacity. Load spectrum plan 2. The whole weighing process The net weight of the raw materials in the weighing silo is converted into an electronic signal according to the weight sensor and transported to the multihead weigher dial. The multihead weigher dial will carry out the calculated net weight of the raw material and the pre-set upper and lower limit values ​​of the net weight. For comparison and identification, according to the PLC control of the water conservancy gate, the feeding into the weighing silo is interrupted.

In addition, the multihead weigher dial compares the measured specific feeding speed (total unloading flow) with the preset feeding speed, and uses PID adjustment to control the feeding equipment, so that the specific feeding speed accurately tracks the preset value. When the feeding water gate is opened to load material into the weighing hopper, the data signal is used to lock the feeding speed, and volumetric feeding is carried out. The multihead weigher dial displays the information on the specific feeding speed and the total net weight of the discharged raw materials. Working circuit schematic diagram 3. Calculation of feeding speed The feeding speed of the multihead weigher (total flow of unloading material) is the damage value of the net weight per unit time. The damage value dt is an accurate measurement of the cycle time. The feeding speed in the case of multihead weigher dial display information can be calculated by the following formula MT=n(d±β*d1)/(td±te) where d——The multihead weigher dial displays information and indicates the value n——Display information display value change number d1——The internal screen resolution of the multihead weigher dial is a data error index, generally β=O. 6td——Precise measurement of cycle time te——Timing deviation index, generally te=0.0014, the total weight is calculated in a detailed total cycle time, the total net weight Gq of the multihead weigher is composed of two parts, namely the multihead weigher dial measurement verification and the stored net weight VA and scale The net weight of the unloaded material that has not been measured and verified during the feeding period of the heavy silo VDGq=VA+VDVA=(VH+￡H)-(VL-￡L)VD=MTL*tF where VH——The upper limit value of the net weight in the weighing silo VD——The lower limit value of the net weight in the weighing silo ￡H——Net weight upper limit value weighing deviation ￡L——Net weight lower limit value weighing deviation MTL——Locked feeding speed tF during loading——The feeding speed MTL locked by the feeding time is still indicated by the change of K net weight display information per second: MTL=K(d±β*d1)/(1±te) The feeding time depends on the total feeding flow MF, MF of the feeding water conservancy gate≈10MTtF=VA/MF A detailed total cycle time is: te=tF+td The average total flow rate is: Mq=Gq/tn Continuously totaling the net weight of each cycle time, the time t=0-- Total net weight of tn.

5. Conclusion In various other electronic machinery and equipment, usually due to the bonding of raw materials, the temperature change of the weight sensor causes the tare weight to change, which in turn leads to a reduction in the accuracy of the system software, but the multihead weigher gets rid of such shortcomings, it is not easy to Temperature shifts reduce weighing precision. The reason is very simple, the feed speed measurement of the multihead weigher is based on the difference of the net weight and not the net weight, so the multihead weigher has a very general application prospect in the software of the fibrous raw material transportation system.

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