The introduction of the digital load cell

Introduction: Digital load cell is a digital weighing instrument with certain applications in industrial, chemical, machine tool, electronics, power, petroleum, medical, scientific research and other fields. With the development of digital load cell skills, digital load cell skills have advanced a lot, and are now well-received in weighing skills.

  First, the difference between digital truck scale and imitation truck scale

Because of the use of digital weighing skills, digital truck scales differ greatly from traditional analog truck scales. First, the interface between the appearance (or computer) of the digital truck scale and the sensor is attributed to the digital communication interface (usually the RS485 communication method). The external signal directly receives the digital signal sent by the sensor. The transmission line can be up to 1200m in length. The interface between the usual imitative truck scale and the sensor is attributed to the imitation interface. The appearance first accepts the imitation signal of the sensor, and then performs A/D change on it before further processing. The transmission interval is usually (20-30) m. Secondly, because the digital truck scale accepts digital signals, the angle difference is adjusted directly in the appearance by software. Instead of the analog truck scale, the potentiometer in the junction box needs to be adjusted to reach the intention of adjusting the angle difference. . These significant differences have resolved that the digital truck scale has many advantages over the imitation truck scale when it is commissioned, making it easier to install and use.

Second, digital sensors and their characteristics

The digital sensor system is a new type of electronic weighing technology based on the traditional resistance strain sensor, which is connected with the integration of modern microelectronics skills and microcomputer skills. It is composed of two parts: the imitation sensor (resistance strain gauge) and the digital change module. The digital module is made up of highly integrated electronic circuits and is based on SMT's external placement skills, including amplifiers, A/D converters, microprocessors (CPUs), memories, interface circuits (RS485) and digital temperature sensors. It has the following features:

First, the digital sensor uses integrated A/D conversion circuit, digital signal transmission and digital filtering skills. The signal transmission distance of the sensor is far, up to 1200m, and the anti-interference ability is strong. The transmission interval of the simulated signal in the digital sensor is extremely short. At the same time, the sensor shell (elastomer) itself is an excellent shield. Only these two characteristics have determined its anti-interference ability, and the sensor stability has been greatly advanced.

  Secondly, it has good confidentiality and anti-cheat function. It can be used to prevent the remote control from cheating. Once it is discovered, it will take the initiative to adopt the error alarm, which effectively guarantees the security and accuracy of the data. The use of imitative sensors for truck scales has been compared to the situation of the device, and several companies with imitation truck scales around the company have been completely equipped with perplexed devices, causing great economic losses. Because the size of the short-cutting device itself is small, and the device is extremely simple, it is not easy to be discovered, which poses a great hidden danger to the safety of the measurement data. Nowadays, the company's large-scale trade scales (except the dynamic rail scale) have been digitally transformed into digital truck scales, which has ensured the safety of metering data and maintained the standard. The economic interests of the company.

  Third, because the digital sensor has the function of actively collecting pre-processing, storage and recollection, and has only symbols, multiple sensors can be connected in parallel to check the condition of each sensor, which is convenient for diagnosis. The digital sensor used by the company today has a single sensor carrying capacity of 50,000 kg. At the beginning, the company's truck scales and track scales are all imitated sensors. The operation status of the equipment is not stable. It is difficult to judge which sensor is in doubt every time. It is only possible to check each one by opening the junction box. The signal status of the root sensor is checked one by one by the exclusion method, and it takes a long time to find the sensor in question. After the inquiry is processed, it is necessary to contact the verification personnel of the Quality Supervision Bureau for verification. The verification fee has changed from normal twice a year to several times. The human, material and financial resources have caused great ruin. The most important thing is to give the company Normal production has a negative impact. Since the digital transformation, many of the questions that have been presented have been dealt with now. The equipment is in excellent condition and the operation is relatively stable. Even after the second phase of the project is put into production, the daily feed volume of the company has doubled. Under the circumstance, the status of the digital sensor is still very stable, and there is no doubt. It proves the superior function of the digital sensor and its primary role in actual production.

   Third, the digital junction box

The digital junction box is the Chinese name for the English Digital J-Box, which uses the "J-BOX" junction box title that mimics the sensor. The junction box that mimics the sensor is the real device for wiring. In addition to the lack of display function, the digital junction box contains the basic functions of the weighing display: expansion, digital/analog conversion and data transmission. The digital junction box can also be regarded as Weighing display without display. In addition, some digital junction boxes today can also display weighing values. Thus, there is no clear boundary between the digital junction box and the weighing display. However, compared with the weighing controller used in the industry, the digital junction box only needs the communication interface, and the input and output ports of the control signal are not connected to the dedicated display or computer through the communication interface RS485 or RS232. The presentation of the digital junction box and the digital sensor, although not seemingly different from the past imitation structure from the outside, does advance in the concept.

Fourth, analysis and comments

The digital system is able to obtain an initial weighing signal for each sensor and can address each sensor individually. In this way, the weighing condition of each sensor can be monitored and analyzed, the online fault detection can be completed; the sensor can be replaced without affecting the calibration; and in a multi-sensor system, when one sensor has a problem, still According to the previous information of the sensor, the system can continue to operate under the condition of ensuring accurate accuracy without replacing the sensor. This has a very important meaning for the condition of the batching system, and these functions cannot be accomplished by the imitation system in which the sensors are used in parallel.

The most important features of the digital system:

At the top of the list, each sensor has its own address, and the operation status of a single sensor can be queried through a communication interface such as RS485.

Second, it is possible to directly obtain the initial output signal of each sensor instead of obtaining a non-analogous signal corresponding to the physical quantity corresponding to the parallel combination of multiple sensors. It is precisely because of these two characteristics that the digital system has truly completed the "smart" function of exploration, identification, and diagnosis.

Third, software that can digitize the sensor (such as temperature, linearity, creep, etc.). In principle, only the sensor's stability is good, and the ideal compensation can be achieved through software. This method has long been proven in the compensation of the sensor, so that the sensor's production energy can be placed primarily on stability.