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  • Ten Daily Electronic Common Sense-Section 141

    What is the HART standard?

    The HART standard (WWW.hartcomm.org) was formulated in the late 1980s.
    In its initial version, the HART field communication protocol was superimposed on a 4-20mA signal to provide two-way communication with intelligent field instruments. And without compromising the integrity of the measurement data.
    In the more than 20 years that the HART standard has existed. The HART protocol has evolved from a simple protocol based on 4-20mA to a protocol that combines current wireless and wired technologies. And has many new features, such as support for security, spontaneous data transmission, event notification, block mode transmission and advanced diagnostics.
    Currently, diagnostic information includes equipment information, information about equipment attachments, and in some cases the actual monitoring process.

    What are the Resistorss allowed for error representation?

    • There are three ways to express the allowable error of the resistor:
      1. Directly expressed in %.
      2. Expressed by letters.
      3. Expressed with I, Il, IIl. I means ±5%, Il means ±10%, IIl means ±20%.

    What are the software anti-jamming measures?

    • Software anti-interference measures in data acquisition
    • Anti-interference measures for abnormal program operation

    What parts of the volt-ampere characteristic curve of the diode can be divided into?

    1. Forward characteristic part:
      • Forward voltage: When the anode of the diode is added with a high potential and the cathode is added with a low potential, the voltage is called forward voltage.
      • Forward characteristics: that is, the characteristics exhibited by the diode when the forward voltage is applied. When u is small, the diode still cannot conduct, this section is called dead IX voltage. That is to say, although a forward voltage is applied to the diode (the potential of the anode A is higher than that of the cathode K), the forward callus is not enough to pass through the barrier layer of the PN junction. So there is still no current (dead zone voltage: germanium tube 0.2 ~ 0.3V; silicon tube 0.5 ~ 0.7V). When the forward voltage exceeds the dead zone voltage, as long as the voltage rises slightly, the current will increase sharply.
    2. Reverse characteristic part: When the diode is applied with a reverse voltage (the anode potential is lower than the cathode potential), a small reverse current is generated. After the LL reverse voltage exceeds a few tenths of a volt, the reverse current no longer increases with the voltage. That is, saturation is reached, and this current is called the reverse saturation current, represented by melons.
    3. Reverse breakdown characteristic part: When the reverse voltage increases to a certain degree of N-4, the reverse current increases sharply. If the reverse current increases to a certain value, the diode will undergo thermal breakdown, which means permanent damage. For example, pay attention to controlling the value of the reverse current, so as not to make it too large. When the reverse voltage is reduced, the diode can resume normal performance.

    What are the five main types of solid-state image sensor devices?

    There are five main types of solid-state image sensing devices: Charge Coupled Device (CCD), Charge Injection Device (CID), Metal-Oxide-Semiconductor MOS Type, Charge Induced Device CPD, and Stacked Camera Devices. Among them, CCD is the most common application.

    What must the CPU do in response to the three cycles of the interrupt?

    1. Turn off interrupts: The CPU first sets the corresponding “priority activation” flip-flops of the responded interrupts to block interrupts of the same level and lower levels.
    2. Breakpoint protection: set the address of the breakpoint (breakpoint address). That is, the content in the current program counter Pc is pushed onto the stack, so that the original program can be continued when the interrupt returns.
    3. Clear the corresponding interrupt request flag bits IE0, IEl, TF0 and TFl.
    4. Load the vector address of the corresponding interrupt source into the program counter PC, so that the program is transferred to the entry address of the interrupt service routine.

    What do you know from the principle of normal operation of junction FETs?

    1. The PN junction between the gate of the junction field effect transistor and the channel is reverse biased. Therefore, the gate current io=0 and the input impedance is high.
    2. The drain current is controlled by the gate-source voltage %s, so the FET is a voltage-controlled device.
    3. Before pre-clamping, that is, when %s is small, the relationship between iD and %s is basically the line’PE. Pre-pinch off the liver, and tend to be full of rain.
    4. In the case of no bias, the D and S poles conduct electricity, and after adding l: negative bias, they lead to IU. Pt-: The special feature of weakening fi, called depletion type, so the junction field effect tubes are all depletion type;
    5. When the P-channel JFET is working, the polarity of the power supply is opposite to that of the N-channel JFET.

    Prompt the connection line and converter do not work the same way, is it wired the same way?

    Different, the role of the port connection line is to connect them to form communication through the agreement of the pins and protocols of both parties.
    The role of the converter is to convert the form of one interface into another form of interface through conversion. However, its pin properties have not changed, such as sending pins are still sending pins. When connecting with the other party, a connection line is still required to connect the two parties.

    What are the main features of the CC2430 chip?

    (a) RF layout
    • Comply with IEEE 802.15.4 standard 2.4 GHz radio frequency transceiver (radio core of CC2420).
    •Excellent wireless receiving sensitivity and strong anti-interference.
    • Few external components, only a single crystal is required for mesh network systems.
    • 7 x7 mm Qi in accordance with RollS standard. P48 package.
    (b) Low power consumption
    • Low current consumption (microcontroller running at 32 MHz, receive: 27 mA, transmit: 27 mA).
    • In power-saving mode, the current consumption is only 0.5 bucket A, and the external interrupt or RTC can wake up the system.
    • Only 0.3 bucket A of current consumption in standby mode, the external interrupt can wake up the system.
    • Fast transition time from low-power mode to active mode, enabling ultra-low average power consumption for low-duty-cycle systems.
    • Wide supply voltage range (2.0-3.6 V).
    (c) Microcontroller
    • High performance and low power consumption 8051 microcontroller core.
    • 32 KB, 64 KB, or 128 KB of in-system programmable flash memory.
    • 8 KB of RAM, 4 KB for data retention in all power modes.
    • Powerful DMA function.
    • Watchdog timer.
    •A MAC timer conforming to IEEE 802.15.4, l general-purpose l6-bit timer and two 8-bit timers.
    • Support for hardware debugging.
    (d) Peripherals
    •Hardware supports CSMA/CA function. the
    • Digital RSSl/LQl support. the
    • Battery monitoring and temperature sensor. the
    • l2-bit ADC with up to 8 inputs and configurable resolution. the
    • Integrated AES security coprocessor. the
    • With two powerful USART interfaces supporting multiple serial protocols. the
    • There are 21 general-purpose I/O port pins, and 2 pins with 20 mA current sink/supply capability. the
    (e) Development tools
    • Powerful and flexible development tools.

    Research and design of underwater wireless sensor networks Compared with terrestrial wireless sensor networks, what are the technical difficulties?

    1. The most important difference between the underwater wireless sensor network and the ground sensor network is the difference in the communication transmission medium. Underwater communication is transmitted through acoustic channels, while on the surface it is transmitted through electromagnetic waves. The acoustic communication channel has serious attenuation and delay, which is prone to underwater ranging errors. This has a great impact on the design of underwater positioning algorithms.
    2. Underwater sensors are susceptible to movement due to other factors such as water flow, and the movement of nodes is usually unpredictable. This causes the position coordinates of nodes to change rapidly, and the coordinates of nodes that have been positioned before are easily invalidated. How to update the node coordinates in real time is a problem that needs to be solved in the underwater wireless sensor network positioning technology.
    3. Since the hardware design of underwater sensor nodes usually adds more sensing components and some underwater transceiver equipment, the cost of underwater sensor equipment is increased. And because seawater has a certain level of saline-alkaline, the exterior design also needs to be corrosion-resistant and waterproof. Underwater sensor nodes are more expensive than surface sensor nodes. Therefore, in terms of node deployment, the deployment of underwater sensor nodes is not as dense as that of ground sensor nodes. This makes node localization more difficult.
    4. Due to the intermittent nature of underwater channels, underwater sensor nodes need to cache data. This has certain requirements on the storage capacity of underwater sensor nodes, and the computing power of sensor nodes is limited. The complexity of the positioning algorithm of the underwater sensor network should be as low as possible, or a distributed positioning algorithm should be used.


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