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 load cells, there are qualitative differences between the old and new national standards. There are mainly S type, cantilever type, spoke type, plate ring type, bellows type, bridge type, column cylinder type and so on.
When it comes to weighing sensors, many people think that they are just sensors that measure the weight of objects. In fact, this is not entirely correct. It has also been applied in many fields. The load cell is similar in principle to the previously introduced pressure sensor, but their shape is different. The load cell used in modern science and technology industry is ubiquitous. The following editor will introduce the classification and disadvantages of load cell.
Load cell classification
Weighing sensors can be divided into eight categories according to the conversion method:
1, resistance strain type
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 deforms. It is mainly composed of 4 parts: elastic element, resistance strain gauge, measuring circuit and transmission cable.
2, hydraulic type
The hydraulic sensor has a simple and firm structure and a large measuring range, but the accuracy is generally not more than 1/100.
It works by using the proportional relationship between the oscillation frequency f of the capacitor oscillation circuit and the distance between the plates d. Capacitive sensors consume less power, are low in cost, and have an accuracy of 1/200 to 1/500.
Digital load cell is a force-electric conversion device that can convert gravity into electrical signals. It mainly refers to a new type of sensor that integrates resistance strain load cell, electronic amplifier, analog-to-digital conversion technology, and microprocessor.
The development of digital weighing sensor and digital metering technology has gradually become the new favorite in the field of weighing technology, and it is emerging in this field with its advantages of simple and efficient debugging and strong ability to adapt to the scene.
5, plate ring type
The structure of the plate-ring type load cell has the advantages of clear stress streamline distribution, high output sensitivity, elastic body as a whole, simple structure, stable stress state, and easy processing. At present, it still occupies a large proportion in sensor production, and the design formula for this structure sensor is not perfect at present.
6, vibration type
After the elastic element is stressed, its natural frequency is proportional to the square root of the force. By measuring the change of 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 sensors: vibrating wire type and tuning fork type.
7, spinning top ceremony
Gyro sensor has a fast response time (5 seconds), no hysteresis, good temperature characteristics (3ppm), small vibration influence, and high frequency measurement accuracy, so it can get high resolution and high measurement accuracy.
includes two kinds of grating type and code disc type. Photoelectric sensors were mainly used in electromechanical scales.
Disadvantages of load cell
The load cell is not perfect, it also has insurmountable shortcomings.
1, the output characteristic is non-linear
The output characteristic of the capacitive load cell is non-linear. Although the differential type is used to improve it, it is impossible to completely eliminate it. Other types of capacitive sensors have linear output characteristics 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 sensor capacitor, making the output characteristic nonlinear.
2, the parasitic capacitance has a large impact
The initial capacitance of the capacitive load cell is small, and the so-called parasitic capacitance, such as the lead capacitance connecting the sensor and the electronic circuit, the stray capacitance of the electronic circuit, and the capacitance formed by the inner plate of the sensor and the surrounding conductor, is large, which not only reduces the sensor The sensitivity, and these capacitances are often randomly changed, will make the instrument work very unstable and affect the measurement accuracy.
3, high output impedance, poor load capacity
The capacity of the capacitive load cell is limited by the geometric size of its electrodes, etc. It is not easy to be very large, generally tens to hundreds of microfarads, or even only a few microfarads. Therefore, the output impedance of the capacitive load cell is high, and therefore the load capacity is poor, and it is easily affected by external interference to cause instability, and even cannot work in severe cases.
Disclaimer: This article is reproduced for the purpose of conveying more information. If there is an error in the source labeling or infringement of your legal rights, please contact us, we will correct and delete it in time, thank you.
Contact Fax： 0552-4070672
Add： Sun Moon Science and Technology Park, No. 985, Xingzhong Road, High-tech Zone, Bengbu, Anhui, China
Force measurement and load cell
Wireless digital sensor
Temperature and pressure sensor
Angle, displacement, speed sensor
Oilfield measurement and control systemWeighing control system
Weighing logistics network solutions
Construction machinery sensor solutions
Oil and gas IoT solutions