High temperature weighing load cell with cylindrical spiral spring inductance coil

High temperature weighing load cell with cylindrical spiral spring inductance coil

Abstract: This article proposes a design scheme for a cylindrical spiral spring inductive coil high-temperature weighing load cell. The high-temperature weighing load cell consists of a cylindrical spiral spring inductance coil, a weighing signal transmission line, and a measurement and adjustment circuit. The cylindrical spiral spring inductance coil is not only the elastic base for carrying weight in high-temperature weighing load cells, but also the inductance strain coil for measuring weight. It is only placed in the high-temperature environment of weighing, and its two ends are connected to the measurement and adjustment circuit located in the room temperature area far away from the high-temperature area using weighing signal transmission lines. This avoids the high temperature resistance problem of resistance strain gauge, Bridge circuit, compensation resistor and other components of resistance strain type high temperature weighing load cell, materials such as strain adhesive and analog weighing signal transmission.

Keywords: cylindrical spiral spring inductance coil; Inductive strain coil; High temperature weighing load cell

1:Introduction

With the improvement of industrial process automation under high temperature conditions, there is an urgent need for high-temperature electronic scales for online weighing and measurement. There are many weighing equipment working in high-temperature weighing environments in metallurgical enterprises. In addition to withstanding impact and eccentric loads during operation, these weighing equipment is also affected to varying degrees by the high-temperature radiation heat and heat transfer from molten steel and steel billets during the rolling process. This is an important reason for restricting the accuracy of high-temperature electronic scales.

High temperature resistant weighing and measuring technology has been one of the technological research directions in the field of weighing technology in China in recent years. High temperature resistance weighing technology needs to focus on solving the high temperature resistance problems of weighing load cells, weighing body devices, and weighing signal transmission. The weighing load cell is the core component of the weighing and measuring device. The most important aspect of high-temperature weighing technology is to solve the problem of high-temperature resistance of weighing load cells. The core of high-temperature resistant weighing load cells is resistance strain gauges.

In the paper "Application of RC and RL Inert Circuits in Scale and load cell Manufacturing" of the 13th Weighing Technology Symposium, I proposed a design scheme for cylindrical spiral spring inductive coil weighing load cells. This scheme is the implementation and application of the spiral spring inductive coil invented in the invention patent "Method for winding spiral spring inductive coils for spring coil load cells" in the design of weighing load cells. The cylindrical spiral spring inductance coil high-temperature weighing load cell is its implementation and application in the field of high-temperature weighing, proposed as a design scheme for discussion.

2:Working principle

The high-temperature weighing load cell consists of a cylindrical spiral spring inductance coil, a weighing signal transmission line, and a measurement and adjustment circuit. Figure 1 is a schematic block diagram.

The cylindrical spiral spring inductance coil is not only the elastic base for carrying weight in high-temperature weighing load cells, but also the inductance strain coil for measuring weight. It is only placed in the high-temperature environment of weighing, and its two ends are connected to the measurement and adjustment circuit located in the room temperature area far away from the high-temperature area using weighing signal transmission lines. The weighing pulse signal output by the cylindrical spiral spring inductance coil is transmitted through the weighing signal transmission line to the measurement and adjustment circuit to complete the weighing measurement.

The resistance strain gauge of the traditional resistance strain type weighing load cell is replaced by the electric induction variable coil, which can avoid the high temperature resistance problem of the resistance strain gauge, Bridge circuit, compensation resistance, strain adhesive and other component materials of the resistance strain type high temperature weighing load cell and the analog weighing signal transmission in the high temperature weighing measurement.

3: System composition

Figure 2 is a block diagram of the system composition: composed of a cylindrical spiral spring inductance coil, a weighing signal transmission line, and a measurement and adjustment circuit chip embedded in software.

1:Cylindrical spiral spring inductance coil

The cylindrical spiral spring inductance coil is an extreme application form of the patented product spiral spring inductance coil. It serves as both an elastic base that carries weight and an inductance strain coil that reflects the size of the weighed weight in a weighing load cell. It is the core component of a high-temperature weighing load cell. There are extremely high requirements for the geometric shape, material, and processing technology of the column, which is a key component of the technical specifications of high-temperature weighing load cells. The column is a mechanical spring, so the design should first follow the design principles of mechanical springs. For example, the stiffness and characteristic curve of the spring should meet the requirements. The stiffness should be large, the deformation of the spring should be small, and the characteristic curve should be linear. As a new technology and device, it requires extensive testing to determine. Because the column works in a high-temperature area, its high-temperature resistance is the high-temperature characteristics of high-temperature weighing load cells. Therefore, in material selection, elastic metal materials with small thermal sensitivity coefficient and stable elastic modulus within the high-temperature range should be selected.

2:Measurement and adjustment circuit chip embedded in software

The measurement and adjustment circuit chip embedded in software consists of a pre input circuit, a loop locking circuit, a variable gate clock circuit, a computer, and software circuits.

The pre input circuit consists of transistors G1, G2, amplifier stage K, and a cylindrical spiral spring inductor coil as an external component of the chip, as well as a weighing signal transmission line. Under the triggering of the pulse signal generated by the loop locking circuit, the weighing pulse signal generated by the cylindrical spiral spring inductance coil is transmitted to the G2 base through the weighing signal transmission line, and output from the R3 and C1 common contacts for amplification stage amplification before being sent to the loop locking circuit. System calibration, temperature compensation, etc. are carried out through a loop locking circuit. Counting and measurement are carried out through variable gates and variable clock circuits, and computer and software control and information processing are carried out.

The measurement and adjustment circuit PCB is shown in Figure 3.

Figure 3 Photos of measurement and adjustment circuit printed circuit board

4:Technical characteristics

In the design scheme, the inductive strain coil integrated with the load cell block elastomer base is used to replace the resistance strain gauge integrated with the load cell block elastomer base, avoiding the technical problems of resistance strain gauge, Bridge circuit circuit, compensation resistance, strain adhesive and other component materials in the resistance strain type high temperature weighing load cell, as well as the technical problems of high temperature remote transmission of analog weighing signals.

Its characteristic is its simple structure, especially for devices working in high-temperature environments, which only consist of an elastic metal body of a cylindrical spiral spring inductance coil, resulting in high reliability, long service life, and good consistency in production and processing performance.

The high-temperature weighing load cell of this scheme can also be used for weighing or measuring force in other special environments.