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    What are the commonly used static calibration devices?

    At present, the commonly used static calibration devices are: piston pressure gauge, lever type and spring dynamometer pressure calibration machine.

    What are the characteristics of the GSM network?

    • The characteristics of the GSM network are manifested in the following aspects:
      1. Spectrum efficiency: Due to the adoption of high-efficiency modulators, channel coding, interleaving, equalization and speech coding technologies, the system has high spectral efficiency.
      2. Capacity: Due to the increase of the transmission bandwidth of each channel (GSM channel bandwidth is 200kHz, the analog is about 25kHz). The same-frequency multiplexing carrier ratio requirement is reduced to 9dB, so the same-frequency multiplexing mode of the GSM system can be reduced to 4/12 or 3/9 or even smaller (the analog system is 7/21). Coupled with the introduction of half-rate speech coding and automatic traffic distribution to reduce the number of handovers, the capacity efficiency of the GSM system (the number of channels per cell per MHz) is 3 to 5 times higher than that of the TACS system.
      3. Voice quality: In view of the characteristics of digital transmission technology and the definition of air interface and voice coding in the GSM specification. Above the threshold, the voice quality always reaches the same level, independent of the radio transmission quality.
      4. Open interface: The open interface provided by the GSM standard is not limited to the air interface, and there may be such as A interface and Abis interface between networks and between entities in the network.
      5. Security: Security is achieved through authentication, encryption and the use of TMSI numbers. Authentication is used to verify the user’s network access rights. Encryption is used for the air interface and is determined by the keys of the SIM card and the network AUC. TMSI is a temporary identification number assigned to a user by a business network to prevent someone from tracking and disclosing their geographic location.
      6. Interconnection with ISDN and PSTN, etc.: Interconnection with other networks usually utilizes existing interfaces, such as ISUP or TUP.
      7. Realize roaming based on the SIM card; roaming is an important feature of mobile communication, which marks that users can automatically enter another network from one network. The GSM system can provide global roaming, and of course some agreements between network operators are required, such as billing. In the GSM system roaming is based on the SIM card identity and the International Mobile Subscriber Identity known as IMSI. This means that the user does not have to carry a terminal device but only his SIM card to enter other countries. The terminal equipment can be leased, and the user number and billing account can still be kept unchanged.

    What is the role of the Acceptance Filter (ACF)?

    The acceptance filter compares the identifier of the received message with the contents of the reception acceptance filter register to decide whether to accept the message.
    The entire message that passes the filter is received and stored in RXFIF0.

    What are the main standards of Industrial Ethernet?

    Industrial Ethernet is to develop appropriate application layer and user layer protocols in accordance with the requirements of industrial control. Make Ethernet and TCP/IP technology truly applicable to the control layer and extend to the scene layer, and use all effective and latest achievements of the IT industry as much as possible in the information layer. Therefore, industrial Ethernet and the application of Ethernet in industry are not the same concept at all. the
    At present, the four main industrial Ethernets have nothing in common with the application layer and user layer protocols except that they obey IEEE 802.3 at the physical layer and data link layer. This is mainly because of their different application fields and development backgrounds.
    If the application field is divided into discrete manufacturing control and continuous process control, and the network is subdivided into equipment layer, I/O layer, control layer and monitoring layer. Then the application positioning of various industrial Ethernets and their related field buses is clear at a glance.
    Among them, the most influential ones, which are mainly used in the field of discrete manufacturing, should be Modbus TCP/IP, EtherNet/IP, IDA and PROFInet. Siemens, which is in a leading position in the global PLC market, spares no effort to promote the combination of PROFIne/PROFIBus. Rockwell Automation and Omron, among others, are working on advancing EtherNet/IP and its sister networks, the CIP-based DeviceNet and ControlNet. Schneider is strengthening its alliance with IDA. In the field of process control, there is only FF HSE. It seems that it is a foregone conclusion that it will be the only industrial Ethernet standard in the field of process control.
    At the monitoring level, OPC DX can be used as a “software bridge” for EtherNet/IP, FF HSE and PROFInet data exchange. Fieldbus Foundation, ODVA and PROFIBUS International (PROFIBUS International. PI), the three major international industrial communication organizations, work together to support the specifications formulated by the DX working group of the OPC (OLE for Process Control) Foundation. Since they each have different priorities, they are unable and unwilling to seek a unified agreement. The way to compromise is to announce support for OPC DX and find an intermediate tool for effective data exchange – a software bridge.

    What are the two most notable features of the Synplicity synthesis tool?

    The two most notable features of the Synplicity synthesis tool are B. E. S. T and Timing Driven (timing driven) synthesis engine.
    These two core comprehensive optimization techniques are complemented by a series of holistic optimization strategies and methods.
    So that their synthesis of the design can achieve a more ideal effect in terms of physical area and operating frequency.

    What are the special features of the TV encoder of the S3C6410 processor?

    With image enhancement engine, the image quality is enhanced with special effects.
    It supports image display modes of different sizes, including full screen, wide screen and original 3 modes.
    Can support analog composite output and S terminal video output at the same time.

    What is piezoelectric ceramic?

    Piezoelectric ceramics are artificially produced isotropic polycrystals. It is a functional ceramic with piezoelectric effect.

    What are the types of rectifier circuits?

    There are three kinds of half-wave rectification circuit, full-wave rectification circuit and bridge rectification circuit.

    What are the two types of errors that the sensor can measure in measuring dynamic changes?

    The error of the sensor in measuring the dynamic change signal can be divided into steady state error and transient error.

    What are the disadvantages of a distributed power system?

    1. The system design is more cumbersome.
    2. The cost is high.


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