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    What are the advantages of a contactless IC card (electronic tag) compared to a contact IC card?

    1. High reliability: There is no mechanical contact between it and the reader, which avoids various failures caused by contact reading and writing. Such as poor contact, rough card insertion, chip falling off, breakdown, bending damage, etc.
    2. Convenient and fast operation: Due to non-contact communication, the reader can operate the card within 10 cm, which is very convenient for users and can improve efficiency.
    3. Anti-collision: There is a fast anti-collision mechanism in the non-contact card, which can prevent data interference between cards. Therefore, multiple cards can be processed in parallel to improve the working speed of the system.
    4. Can be suitable for a variety of applications: the storage structure of the card makes it possible to realize a multi-purpose card, and can be applied to different systems through the setting of passwords and access conditions.
    5. Good encryption performance: The serial number of the non-contact IC card is unique and cannot be changed by the manufacturer. Each sector in the card has its own operating password and access conditions, and a two-way authentication mechanism is used between the card and the reader. And all data in the communication process is encrypted, so it is very suitable for applications such as electronic wallets, highway automatic toll collection systems and bus automatic ticketing systems.

    OSPF has several types of protocol packets?

    1. Hello packets: sent periodically to discover and maintain OSPF neighbor relationships.
    2. Database Description message: Describes the summary information of the local LSDB, which is used for database synchronization between two routers.
    3. Line State Request message: request the required LSA from the other party.
    4. Line State Update message: send the LSA it needs to the other party.
    5. Line State Acknowledgment message: used to confirm the received LSA.

    What are the two main types of training algorithms for MLP?

    One type chooses the neural network during the learning process; the other type does not.
    The first type of algorithm is called a constructive algorithm. Most artificial neural network applications use large-scale fully connected networks, where the algorithm sets the value of unnecessary parts to close to zero. There are techniques to remove these links afterward.
    The non-constructive algorithm just picks out all the tunable parameters of the neural network, including back-propagation, which is now widely used. At present, the RPROP algorithm is generally chosen because it has better effect and is easy to implement.

    What is the FCC defining a digital device?

    An unintentional radiator (device or system) that generates and uses a time signal or pulse of more than 9000 cycles and associated digital techniques.
    Including telephone equipment using digital technology, as well as those devices or systems that generate and use radio frequency energy to perform digital processing functions.
    For example: electronic computers and equipment for electronic processing, transmission, recording, filtering, sorting, storage, forwarding or transmission.

    What are the methods of current transformer ratio test?

    A current transformer is a special transformer specially used to transform current.
    Under normal operating conditions, its secondary current is substantially proportional to the primary current. And when the connection direction is correct, the phase difference between the secondary current and the primary current is close to zero.
    As an important equipment in the power system, it is very important to carry out the electrical performance test of the current transformer. For the current transformer, the transformation ratio test is an indispensable test item, and the transformation ratio of the current transformer is related to the accuracy of measurement and the reliability of protection.
    The on-site transformation ratio inspection of the current transformer generally adopts the current method, and the current method is used to measure the transformation ratio of the current transformer. In fact, it simulates the actual operating conditions under the condition of rated current, which is an ideal test method with high measurement accuracy.
    However, with the continuous development of the power system, the capacity of a single generator has become larger and larger, and its export current has reached tens of thousands of amperes. For example, for an 800MW generator set, the rated voltage is 20kV and the rated current is: 800/(20×31/2)=23.094kA. The primary current of the corresponding current transformer is very large. If using the amperometric method to measure the transformation ratio of a current transformer with a primary current of tens of thousands of amperes, it is difficult to do it on site: First, it is difficult to achieve a high rated current (a large-capacity voltage regulator is required). Second, the required standard current transformer or current booster is bulky and expensive. If the primary current of the current transformer under test is reduced for the test, the ratio error will be very large, and the test will be meaningless.
    Therefore, the method of measuring the transformation ratio of the current transformer by the current method is more and more limited in the construction site. On the basis of the current method, the author introduces another test method for the transformation ratio of the current transformer – the voltage method. This method is suitable for the inspection of the transformation ratio of the current transformer at the construction site. The voltage method has the advantages of a wide range of applications, less equipment and simple equipment, and is a simple and convenient test method.

    What is the external photoelectric effect?

    Under the action of light, the electrons in the object escape from the surface of the object, and the phenomenon of outward emission is called the external photoelectric effect.

    What are the MC9S12XE series microcontroller features?

    • The XGATE coprocessor can virtualize external devices and improve overall performance.
    • Extended programmable EEPROM.
    • System-level support for memory protection units, with manager and user modes.
    • Sl2XCPU at 50MHz bus speed.
    • Memory Protection Unit (MPU).
    • Loop control/full swing Pierce oscillator.
    • Enhanced interrupt module.
    • Non-multiplexed external bus interface (EBI).
    • Non-multiplexed external bus interface (EBI).
    • Enhanced Capture Timer (ECT).
    • Periodic Interrupt Timer (PIT).
    • Real-time interrupt (RTI).
    • Synchronous periodic interrupt (API).
    • Pulse Width Modulation (PWM).
    • MSCAN module.
    • Serial Peripheral Interface (SPI).
    • Serial Communication Interface (CSCI).
    • Background Debugging (BDM) Debugger (xDBG).
    • On-chip voltage regulator.

    What is the way the crystal oscillator of the LPC2000 series ARM generates a clock?

    The crystal oscillator of the LPC2000 series ARM can use an external clock source, or an external crystal and an on-chip oscillator circuit to generate the clock.

    In general, what are the main factors affecting the size of the strain limit?

    In general, the main factors affecting the size of the strain limit are the properties of the binder and the base material. As the true strain of the structure increases, its ability to transmit deformation gradually decreases. Makes the indicated strain no longer vary linearly with the true strain.

    What are the two major categories of memory?

    From the point of view of the access function of memory, there are two types of memory: Read Only Memory (ROM) and Random Access Memory (RAM).


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