November 19, 2021

Technical Principle of Load Cell


When it comes to the principle and technology of load cells, many people think that this is just a load cell that measures the weight of an object. In fact, this is not entirely correct. It has also been applied in many fields. The principle of the load cell is technically similar to the pressure load cell introduced before, but their shape is different. Let me briefly explain the application of the principle and technology of the load cell!


Weighing load cells used in modern science and technology industries are ubiquitous. The principle of the load cell is a device that converts the quality signal into a measurable electrical signal output. In the basic concepts and evaluation methods of the main technical indicators of the load cell, there are qualitative differences between the new and the old national standards. There are mainly S type, cantilever type, spoke type, plate ring type, bellows type, bridge type, column cylinder type and so on.


The principle of the load cell, the working principle of the load cell has two basic structural types: linear and rotary (disc type). The load cells are composed of a sliding ruler and a fixed length (linear type) that can move relatively or a rotor and a stator. (Rotary) composed. These two types of weighing induction synchronizers are manufactured using the same process method.


The load cell first uses an insulating erecting agent to glue the conductive copper foil (thickness 0.04~0.05mm) on the substrate of non-magnetic material such as low carbon steel or glass, and then according to the design requirements, use the photolithography or chemical corrosion process to Copper foil is etched into plane windings with different zigzag shapes, which are generally called printed circuit windings. The fixed-length and sliding-length, the distribution of windings on the rotor and stator are different. The windings on the fixed length and the rotor are continuous windings, and the windings on the sliding scale and the stator are segmented windings. The segment windings are divided into two groups, which are arranged in a space with a difference of 7r to the left. The working principle of the load cell is also called sine and cosine windings.


The continuous winding and the segment winding of the induction synchronizer are equivalent to the primary winding and the secondary winding of the transformer, and work on the principle of alternating electromagnetic field and mutual inductance.


According to the classification of load cells, load cells can be divided into eight categories according to the conversion method: resistance strain gauge is the most widely used load cell. It uses the principle that the resistance of the resistance strain gauge changes when it is deformed. It is mainly composed of 4 parts: elastic element, resistance strain gauge, measuring circuit and transmission cable.


The hydraulic hydraulic load cell has a simple and firm structure and a large measuring range, but the accuracy is generally not more than 1/100. The capacitive type uses the proportional relationship between the oscillation frequency f of the capacitor oscillation circuit and the electrode plate spacing d to work. Capacitive load cells consume less power, are low in cost, and have an accuracy of 1/200 to 1/500.


The principle of digital digital load cell is a force-electric conversion device that can convert gravity into electrical signals. It mainly refers to a combination of resistance strain load cell, electronic amplifier, analog-to-digital conversion technology, and microprocessor. New load cell.


The development of digital weighing load cell and digital metering technology has gradually become the new favorite in the field of weighing technology, which is emerging in this field with its advantages of simple and efficient debugging and strong ability to adapt to the scene.


The structure of the plate-ring plate-ring load cell has the advantages of clear stress streamline distribution, high output sensitivity, integrated elastic body, simple structure, stable stress state, and easy processing. At present, it still occupies a large proportion in load cell production, and the design formula for this structure load cell is not perfect at present.


After the vibrating elastic element is stressed, its natural vibration frequency is proportional to the square root of the force. By measuring the change of the natural frequency, the force of the measured object acting on the elastic element can be obtained, and then its mass can be obtained. There are two types of vibration load cells: vibrating wire type and tuning fork type.


The gyroscope load cell has a fast response time (5 seconds), no hysteresis, good temperature characteristics (3ppm), small vibration influence, and high frequency measurement accuracy, so it can obtain high resolution and high measurement accuracy.


The photoelectric type includes two kinds of grating type and code disc type. Photoelectric load cells have been mainly used in electromechanical scales. Disadvantages of load cells.


The load cell is not perfect. It also has insurmountable shortcomings. The output characteristic of the non-linear capacitive load cell is nonlinear. Although the differential type is used to improve it, it is impossible to completely eliminate it. The output characteristics of other types of capacitive load cells are linear only when the edge effect of the electric field is ignored. Otherwise, the additional capacitance generated by the edge effect will be directly superimposed on the load cell capacitor, making the output characteristic nonlinear.

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