A weighing instrument is a device that displays the weight and status of an object being measured, commonly referred to as a weighing display. Originally, electronic weighing instruments were analog devices, consisting of components such as an error amplifier, a reversible motor, a balanced bridge, an excitation power supply, a dial, and a pointer. These early systems operated based on the principle of an automatic balance electronic potentiometer, but they had slow weighing speeds, limited functionality, and low accuracy, which led to their gradual obsolescence. Today, most weighing displays are digital, offering greater precision, speed, and versatility. The structure of an electronic weighing instrument Working Principle Digital scale instruments come in various types, one of which is illustrated in Figure 1. The digital receiver receives electrical signals from the load cell. These signals can be either analog or digital, with analog voltages typically ranging in the tens of millivolts. The circuit diagram of the digital display is shown in Figure 2. The excitation power supply provides power to the load cell and also supplies the reference voltage for the A/D (analog-to-digital) conversion unit, usually with a stability of 0.1% or higher. The amplification unit typically uses a measuring amplifier configuration to receive and amplify the signal from the load cell, with gains often reaching hundreds of times. The filtering unit helps eliminate electrical noise from both external sources and the amplifier itself. The A/D conversion unit then converts the analog signal into a digital format, usually with 14 bits or more of resolution. The data processing unit, centered around a microprocessor and supported by peripheral chips, handles tasks such as data collection, computation, and storage under program control. Finally, the processed data is sent to the appropriate interface for output. The display unit presents the weight value and status in numerical or graphical form and may communicate with external devices through its interface. Schematic Diagram of the Weighing Instrument – Circuit Diagram Performance Characteristics The performance of digital instrumentation includes five key aspects: metrological performance, functionality, environmental adaptability, safety, and reliability. Compared to general-purpose digital weighing instruments, modern digital displays offer five main features: 1) built-in sensor excitation power supply for ease of use; 2) ratiometric A/D conversion and frequency multiplication technology, ensuring long-term metrological stability; 3) software that realistically simulates weighing characteristics like vibration, air balance changes, and material drop, resulting in fast, accurate, and stable readings; 4) configurable parameters such as tare, zero tracking, calibration, maximum capacity, and indexing, making the instrument highly versatile; 5) output interfaces that allow connection to various external devices, enabling convenient system integration. Accuracy Levels According to OIML Recommendation No. 3, non-automatic scales are classified into four accuracy grades. In China, electronic weighing instruments are also divided into four levels—designated as I, II, III, and IV—based on their accuracy. The maximum permissible error for each class is 0.7 times the tolerance of the corresponding instrument class. Netizens explain the basic architectural principles of scale instruments The architecture of a weighing instrument is actually quite simple. A power supply provides energy to all components. An AD (analog-to-digital) module amplifies the analog signal from the sensor and converts it into a digital signal. A central processing unit (MCU), or single-chip microcomputer, processes this data. The weight signal is converted and decoded into a readable format for the display screen. Most instruments also include a keyboard circuit to accept user input, and many feature a parallel print port, micro-drive, RS232 or RS485 interface for communication with host computers or other devices. Some models support a 4–20mA current loop interface for industrial control applications, while high-end versions may have CAN bus or Ethernet connectivity. Although some instruments also include a USB interface, it is rarely used due to its limited transmission range, so fewer scale instruments feature this option. Stay tuned for more updates Tag: Electronic Weighing Instrument, Load Cell, Keyboard Circuit, Print Port, Accuracy Level Previous: After vehicle repair, attention should be paid to running-in. Next: Procedures for the use, maintenance, and upkeep of die-casting molds Eyelet Tool,Grommet Tool,Eyelet Pliers,Eyelet Kit NINGBO ZONGLAN MECHANICAL AND ELECTRICAL EQUIPMENT MANUFACTURE CO., LTD , https://www.zonglaneyelet.com