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RC、RL The Application of Inert Circuit in the Manufacturing of Weighing Instruments and Load Cell

Views: 6     Author: Site Editor     Publish Time: 2023-06-15      Origin: Site

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Abstract: This article introduces the principles, system composition, and technical characteristics of RC and RL inert circuits and their corresponding R and L Load cells, with a focus on the application of spiral spring inductance coils as L components of RL inert circuits in the manufacturing of weighing instruments and load cells. Introduced the application product of the spiral spring inductance coil "Digital Display Human Body Height and Weight Measurement Instrument". Explored the application prospects of spiral spring inductance coils in the manufacturing of weighing load cells.


1:Introduction

Ningbo Saintbond designed a technical solution for manufacturing resistance, capacitance, and inductance sensors using RC and RL inert circuits in the utility model patent "A load cell" authorized in 2001. RC inert circuits have been widely used in the manufacturing of household weighing instruments in the past decade. The application principle of RL inert circuit in sensor manufacturing has been disclosed by Ningbo Saintbond in the invention patent "Method for Winding Spiral Spring Inductive Coils for Spring Coil Load cells" ; As an application of the spiral spring inductance coil of the L component in the RL inert circuit in length (displacement) measurement, a research sample of a digital human height measurement instrument has been developed. We are currently seeking to negotiate production matters with relevant enterprises. The application of spiral spring inductance coils as weighing (force measurement) sensors is still in the exploration, research, and experimental stage.


2:Circuit principle

R. C and L are the three basic passive components in electronic circuits, consisting of RC or RL series connected circuits. The inert circuit waveform generated by the square wave pulse signal, namely the periodic transient circuit waveform, is integrated into the DC voltage output through the integration circuit composed of R and C, and the change in DC voltage is related to the sensitive component R (such as a resistance strain gauge) The variation of the measured physical quantity sensed by C or L (such as a spiral spring inductance coil) is proportional, and the purpose of measuring the measured physical quantity is achieved by measuring this voltage.

 

3:System composition

The inert circuit and pulse conversion circuit are composed of a square wave pulse signal source, a fixed resistor, inductor, and capacitor element in series with a sensitive element in the resistor, inductor, and capacitor sensitive element. The output end of the square wave pulse signal source is connected to one end of the inert circuit and the control end of the pulse conversion circuit, and the other end of the inert circuit is grounded, The common contact point of an inert circuit is the connection between the output end and the input end of the pulse conversion circuit, and its output end is connected to other display components or data processors. Figures 1 and 2 show the circuit diagrams of the group cost system.

图片2图片two

                                          Figure 1                                                  Figure 2


Figure 1 shows the circuit schematic diagram of an inert circuit sensor composed of a fixed resistor R2 and a sensitive element inductance L1.

The load cell consists of a square wave pulse signal source, a fixed resistor, a sensitive element inductance, and a pulse conversion circuit. The square wave pulse signal source is composed of a square wave oscillation generator IC1, resistors R1, R5, crystal JZ, capacitors C1, C2, and transistor G1. The inert circuit is composed of a sensitive element inductor L1 and a fixed resistor R2 in series. The pulse conversion circuit consists of a transistor G2, analog switch IC2, resistors R3, R4, and capacitor C3. The output of the square wave pulse signal source is connected to one end of the inert circuit by the emitter e of G1 on pin 7 of IC1. The output end of the inert circuit is fixed with a resistor R2 and the common point of the sensitive element inductance L1, which is connected to the base b of the input terminal G2 of the pulse conversion circuit. The other end of the inert circuit is grounded, The control input terminal of IC2, pin 13, is connected to pin 7 of IC1 in the square wave pulse signal source, and the output terminals R4 and C3 of the pulse conversion circuit are connected to other display components or data processors through common contacts.


4:Technical characteristics

The circuit structure is simple, the combination is flexible, and the production cost is low. By using the same conversion circuit with different sensitive components such as resistors, inductors, or capacitors and their corresponding inert circuits, corresponding resistance, inductance, or capacitance sensors can be formed. It provides the possibility for the integration, miniaturization, intelligence, and versatility of load cells.


5: Application effect

The utility model patent "A Sensor" introduced above was applied by the author on May 26, 2000 and February 17, 2001,Daily authorization. Later, due to the application for an invention patent in 2004 titled "Method for Winding a Spiral Spring Inductive Coil for Spring Coil Sensors" and the invention of a Spiral Spring Inductive Coil in the patent, the patent right was abandoned. Based on relevant information and my limited understanding of relevant enterprises, RC inert circuits, including those with R (resistance strain gauge) as the sensitive element and C as the sensitive element, have been widely used in the manufacturing of household weighing instruments in the past decade.

The Application and Prospects of RL Inert Circuit: The spiral spring inductor coil (as the sensitive element L of RL inert circuit) invented by the author in the invention patent "Method for winding spiral spring inductor coils for spring coil sensors"  in 2004 has broad application prospects. The spring coil sensor composed of spiral spring inductance coil uses the mechanical and electronic properties of the mechanical spiral spring itself to use it as both a Machine element and an electronic component (variable inductance coil) to form a spring coil sensor that outputs a digital quantity proportional to the measured value. It endows mechanical spiral springs with new functions and application fields. As a new and practical basic interface device for mechatronic conversion, it can be directly or through its manufacturing into a series of application products for different purposes, and applied in corresponding control or measurement occasions.

Since the spring inductance coil of the spring coil sensor is a sensitive element that has sensitive effects on almost all mechanical quantities and some thermal quantities, in principle, the spring coil sensor can convert and measure the measured values such as displacement, force, vibration, acceleration, noise, angle, flow rate, flow rate, etc. By changing the size and performance of the spring coil winding, the function and purpose of the spring coil sensor can be changed. Widely used in various fields such as weighing instruments, transportation represented by automobiles, modern equipment industry, traditional industry, logistics, measurement, and instrumentation.


6:Application of Spring Coil load cells

6.1: Spring coil sensor chip

At present, the development and design of a universal sensor chip circuit has been completed, which integrates sensitivity, measurement, adjustment, and display, and has functions of weighing, measuring force, and measuring displacement (length). The chip can be equipped with spring inductance coils with different functions to form terminal application products for corresponding purposes.


6.2: Digital display human height measuring instrument

Adult height range: 62cm-195cm, with a graduation value of 2mm;

The baby's body length ranges from 2cm to 60cm, with a graduation value of 2mm.

The digital display human height measuring instrument is a specific application product of spring coil sensors in the field of length (displacement) measurement, with simple structure, small volume, and low production cost. It can be integrated with a household weight scale to become a commonly used health measurement device for families. The health (obesity) index of a person is calculated and displayed based on the measurement value of height and weight. The price is set at around 200 yuan, which is 1/20 of the imported ultrasound based height and weight meter and 1/40 of the imported laser based height and weight meter. The "Digital Display Body Height and Weight Measuring Instrument" that can enter families is still a blank, suitable for families, kindergartens, primary and secondary schools, grassroots healthcare, fitness, and elderly care institutions. Figure 3 is a research sample diagram of a spring coil sensor digital display human height measuring instrument, and Figure 4 is a schematic diagram of height measurement.


图片3

                                                                      Figure 3


图片4

                                                                   Figure 4


6.3: Discussion on the design of coil spring inductance coil weighing (force measurement) sensors

As is well known, spring dial scales and spring digital scales have low accuracy and cannot generally be used as commercial or industrial scales. The author believes that the main reasons for this are: firstly, the performance of the spring itself, including the characteristics of the spring material, the shape of the spring, etc. Secondly, the use of spring methods often causes excessive deformation of the spring. For example, the spring dial scale must allow the variable length of the spring to reach a certain amount to meet the needs of the dial indexing. If the spring coil is made of special elastic metal material and made into a cylindrical spiral spring coil as shown in Figure 5, the stiffness of the cylindrical spiral spring coil is adjusted so that the cylindrical spiral spring coil only undergoes small deformation during weighing (force measurement), and the inductance of the cylindrical spiral spring coil also correspondingly only undergoes small changes. This small change in inductance is sent to the measurement and adjustment circuit for "processing", It can improve the accuracy level of the coil spring inductance coil weighing (force measurement) load cell.

This cylindrical spiral spring inductance coil is not only a base that carries the weight of the weighed object, but also an inductance coil that can produce changes in inductance under the weight of the weighed object. This change in inductance reflects the weight of the weighed object.

A base that carries the weight of the object being weighed, equivalent to the base of a strain gauge sensor; The change in inductance is equivalent to the change in strain resistance value of a strain gauge sensor; The inductance coil is equivalent to a resistance strain gauge of a strain gauge sensor.

This cylindrical spiral spring inductor coil can be manufactured by adding a medium to the center of the coil to increase its inductance

Apply shielding paint on the surface of the coil to shield against external electrical or magnetic interference.

图片5

                  Figure5

Replacing L1 in Figure 1 with the cylindrical spiral spring inductance coil in Figure 5 becomes the cylindrical spiral spring inductance coil weighing (force measurement) sensor. The analysis method is the same as that in Figure 1, and is omitted here.

This design proposal has been proposed for discussion with experts, and the feasibility of the proposal is subject to their guidance. I sincerely hope to receive support and assistance from the business community to jointly research, experiment, and develop.


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