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    Briefly describe the working principle of the DS11-2 elevator load cell?

    The DS11-2 elevator weighing sensor is used in conjunction with a permanent magnet (round magnetic steel). When the magnetic field strength at the sensor probe is greater than a certain value, the trigger inside the sensor will flip.
    The output level state of the Hall switch is also reversed, the indicator light is on, and a high-level signal is output; otherwise, the indicator light is off, and a low-level signal is output.
    Using this principle, it can provide light load, full load, overload and other switching signals for the elevator.

    What are the components of the central computer system?

    It consists of a host computer, a communication controller (also known as a pre-processor) and peripheral devices.  
    (1) The host, also known as the central processing unit, consists of a central processing unit (CPU), main memory, input/output devices and other peripheral devices, and its main function is to process data.  
    (2) The communication controller is the interface between the data circuit and the computer system. It is used to manage all communication lines connected to the data terminal, receive data signals from remote DTEs, and send data signals to remote DTEs. For example, the asynchronous communication adapter (such as UART) in the microcomputer and the network card in the digital baseband network are the communication controllers.

    What are the main power losses of inductive switching power supplies during product operation?

    1. The conduction loss of the built-in or external MOSFET is mainly related to the duty cycle and the on-resistance of the MOSFET.
    2. Dynamic loss, including the switching loss when the high-side and low-side MOSFETs are turned on at the same time, and the power loss of the switching capacitor of the driving MOSFET, are mainly related to the input voltage and switching frequency.
    3. The static loss is mainly related to the leakage current inside the IC.

    What is the Mie theory?

    The scattering phenomenon of monochromatic electromagnetic waves caused by conductor spheres in isotropic media can usually be described by Mie theory.
    Since the sphere is assumed to be a conductor, the problem involves both refraction, reflection, and absorption phenomena. In fact, after the electromagnetic wave collides with the sphere, a part of it is injected into the conductor. That is, part of the energy of the electromagnetic field is absorbed by the sphere. When the medium is a dielectric, it can be found simply by setting the conductivity of the sphere to zero. 
    Although Mie theory was originally developed from a single scattering sphere, it is easily generalized to the form of a large collection of scattering spheres. Suppose a large number of spheres of the same size and composition are randomly distributed and are farther apart from each other than the wavelength of a monochromatic wave.
    Under this condition, although the beam scattered by each sphere cannot be expected to have a consistent phase relationship, the sum of the scattered energies can be obtained by adding the energies scattered by each sphere. 
    Mie theory mainly studies the scattering of electromagnetic waves when the wavelength of the electromagnetic wave is approximately equal to the size of the scattering sphere. Therefore, the Mie theory is very important to study the diffraction phenomenon caused by the random floating of small particles in the atmosphere or ocean.

    What points should I pay attention to when using the antenna in the room system?

    1. Try to choose a broadband antenna: In the process of selecting an antenna for an indoor sub-system, the frequency band of the antenna should include the working frequency bands of wireless standards such as GSM, CDMA, WCD-MA, TD-SCDMA, WLAN, and LTE. That is to say, including all mobile communication frequency bands from 800 to 2500 MHz. The choice of broadband can avoid the transformation of the antenna and feeder when adding a new wireless system, and can also avoid the problems of repeated entry and repeated construction.
    2. Diversity and beamforming are not considered: due to the narrow space and large penetration loss in the indoor environment, using diversity technology is like shooting mosquitoes with anti-aircraft guns. The improvement of system performance is not obvious, but it increases the system cost. Generally, the antenna density of the indoor sub-system is large, coupled with the complex indoor environment, the user density is large. Using beam shaping is like using a water gun to spray someone in the crowd, it may not be able to spray accurately, it is better to use a basin of water to directly spray it, but it can spray that person. Therefore, the use of diversity and beamforming technology indoors is not effective and has little meaning. Although TD-SCDMA supports smart antenna beamforming, it does not use beamforming in indoor environments.
    3. Select a vertically polarized antenna: when the horizontally polarized radio wave propagates close to the surface of the ground object, a polarization current will be generated. Affected by the impedance of ground objects, heat energy can be generated, thereby rapidly attenuating radio wave signals. However, vertically polarized radio waves are not easy to generate polarization currents on the surface of ground objects, so as to avoid substantial attenuation of energy and ensure that wireless signals can effectively propagate in complex indoor environments. Therefore, in the indoor environment, the antenna generally adopts the vertical polarization method.
    4. The selection of the antenna should adapt to the characteristics of the scene: the omnidirectional ceiling antenna is used in the center of the indoor room. The wall-mounted panel directional antenna is mounted on the wall in a rectangular environment. High-gain directional antennas and leaky cables are generally used in long and narrow enclosed spaces such as elevator shafts, tunnels, and subways. Yagi antennas are suitable for use in environments with only one system. If multiple systems are combined, a broadband high-gain directional antenna, such as a broadband log-periodic antenna, needs to be used.

    What is a conductivity type chemical sensor?

    Conductivity chemical sensors are measuring devices that convert chemical quantities into conductivity signals under an applied voltage.

    What are the main performance characteristics of TJAl040?

    • Fully compliant with IS011898 standard;
    • High speed (up to 1Mb/s);
    • Very low electromagnetic radiation (EME);
    • Differential receivers have a wide common mode range and are resistant to electromagnetic interference (EMI);
    • Transceiver in unpowered state will be disconnected from bus (zero load);
    • Input stage compliant with 3.3V and 5V devices;
    • If a separate terminal is used, the voltage source can stabilize the recessive bus level (improve EME);
    • At least 110 nodes are connected;
    • The standby mode with extremely low current consumption has the function of waking up through the bus;
    • Dominant timeout function for sending data;
    • Protect the bus pins in the automotive environment against instantaneous interference;
    • Prevent the bus pins and pin SPLIT from short-circuiting to the battery and ground;
    • Thermal Protect.

    Which types of circuits can be divided into source drive circuits depending on whether a digital-to-analog converter (DAC) is included in the circuit?

    Source drive circuits can be divided into analog source drive circuits and digital source drive circuits according to whether a digital-to-analog converter (DAC) is included in the circuit.

    What are the advantages of the LIN system?

    1. System flexibility
    2. Message routing
    3. Multicast
    4. Bit rate
    5. Single host – no arbitration
    6. Error demarcation and fault delimitation
    7. Connection

    What are the inverter operation control functions?

    1. Starting frequency
    2. Acceleration and deceleration time
    3. Jog operation
    4. DC braking


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