The measurement sensor manufacturer talks about the use prin
As one of the tools for human-machine communication, the sensor can capture various information of the machine in the process of operation, and provide technical and theoretical basis for people's next decision. At the same time, it can provide accurate technical support in product design and parameter research.
With the advancement of technology, the application of sensors has become more and more extensive, and it has penetrated into various fields.
Force sensor composition
The function of the sensor is generally to convert the measured non-electricity into a power output. It is mainly composed of four parts: a sensitive component, a conversion component, a measuring circuit and an auxiliary power supply.
(1) Sensitive components: In the sensor, the main function is to feel the measured change, and at the same time transform the measured into an intermediate variable that is easy to transform into electricity. Such as diaphragm pressure sensor, its sensitive piece is an elastic diaphragm, its function is to transform the pressure signal into the deformation of the diaphragm, for the next
Prepare the output of the step signal.
(2) Conversion element: The sensor converts the intermediate non-electricity output of the sensitive element into a quantity that can be utilized by the sensor through the conversion element. It mainly uses some physical, chemical or biological effects to achieve this.
For example, the conversion element of a diaphragm type pressure sensor converts the deformation of the elastic diaphragm into a resistance value by utilizing the resistance strain effect, that is, the principle that the resistance of the metal conductor or the semiconductor changes as the mechanical deformation thereof changes. Variety.
(3) Measurement circuit: It is often difficult to directly display, record, and process the output of the conversion component. It needs to be further converted into an electrically usable signal. The measurement circuit is used to complete this function.
For example, the measuring circuit in the strain gauge pressure sensor is a bridge circuit, which can convert the resistance value of the strain gauge output into a voltage signal, and after amplification, can drive the working of the recording device and the display instrument.
(4) Auxiliary power supply: Some sensors require an auxiliary power supply to provide signals in addition to the circuit power supply.
2, the basic requirements of the load cell
There are many types of sensors used in machinery, but resistive sensors are used more.
The internal circuit of the resistance strain gauge type load cell is generally a bridge circuit. The resistor acts as a conversion element, and the change in resistance value is ultimately output as a signal.
Due to its simple structure, good linearity and stability, and high output accuracy, it has received more and more attention in practice. The sensitive component used is an elastic test component, and the body is an elastomer. The structural shape and related dimensions of the elastomer have a great influence on the performance of the load cell.
If the elastomer design of the load cell is unreasonable, no matter how high the processing precision of the elastomer and the quality of the attached strain gauge, the load cell is difficult to achieve high force measurement performance.
Therefore, the structural form of the elastomer is critical in the selection of the load cell.
The sensor's circuit works:
The design of the elastomer is basically within the scope of the mechanical structure design, but the structure is different from the ordinary mechanical parts and components due to the need of the force measurement performance.
In general, ordinary mechanical parts and components only need to meet the strength and stiffness under a sufficiently large safety factor, and the stress distribution on the parts or components under stress conditions is not strictly required.
However, for the elastomer, in addition to the mechanical strength and rigidity requirements, it is necessary to ensure the stress (strain) of the strain gauge portion (hereinafter referred to as the "patch portion") and the load on the elastomer. Force measurement) maintains a strict correspondence; at the same time, in order to improve the force
The sensitivity of the sensor's force should also be such that the patch reaches a high level of stress (strain).
The elastomer of the load cell must meet the following two requirements during the selection process:
(1) The stress (strain) of the patch should be strictly related to the measured force; it can truly reflect the deformation of the tested component.
(2) The patch site should have a high level of stress (strain). Timely reflection of the force of the components.
In order to meet the above two requirements, the principle of “stress concentration” is often applied to the selection of elastomer components of the load cell to ensure that the stress (strain) level of the patch is high and maintains a strict correspondence with the measured force. To improve the force sensitivity and force measurement of the designed load cell
The principle of “stress concentration” that improves the stress (strain) irregular distribution:
During the testing of mechanical parts or components, stress (strain) is generally considered to be regularly distributed on the part or component. If the shape of the part or member does not change, it is not necessary to consider the problem of irregular stress (strain) distribution.
In fact, in the design of mechanical parts or components, the problem of irregular distribution of stress (strain) is not considered, but is included by the safety factor in the strength calculation.
For the load cell, it measures the strain of the patch on the elastomer by the strain gauge to measure the measured force.
To ensure that the stress (strain) of the patch portion is strictly related to the measured force, it is actually to ensure that the stress (strain) of the patch on the elastomer is distributed according to a certain rule when the load cell is stressed. , that is, according to the variation of the measured members.
In practical applications, the factors that have a greater influence on the stress (strain) distribution of the elastomer patch are mainly the changes in the stress conditions of the elastomer.
The change of the elastic force condition means that when the magnitude of the force applied by the elastic body is constant, the action point of the force changes or the contact condition of the elastic body with the adjacent loading member and the bearing member changes.
If this situation is not considered in the design of the elastomer structure, it may cause irregular changes in the stress (strain) distribution on the elastomer.
3. Application of new technology in sensors
(1) Development and application of new materials, new processes and new technologies
Semiconductor materials occupy a large technical advantage in sensitive technology. Semiconductor sensors not only have high sensitivity, fast response, small size, light weight, but also easy integration, and will still occupy a dominant position;
Functional ceramic materials with certain chemical composition, molding and sintering, the most important feature is heat resistance, which has great potential in the development of sensitive technology. At the same time, the precision micro-machining technology and electrostatic sealing technology of semiconductor are applied in Sensor manufacturing can greatly improve sensor performance
(2) Integration, multi-dimensional, multi-functional and intelligent development of sensors
Using integrated processing technology, the components of the sensor are fabricated on the same chip, so that the sensor has the advantages of small size, light weight, high production automation, low manufacturing cost, high stability and reliability, short installation and debugging time, etc. .
Using electronic scanning technology, multiple sensor units can be combined to study multi-dimensional space problems, such as CT technology. Intelligent sensors can also integrate data collection, storage, processing, etc. .