Ten Daily Electronic Common Sense-Section 13

The difference between inductance and resistance：

The inductor belongs to the passive component and only works when the current passes.
Its function is to convert the alternating current into direct current, and then filter out some of the noise waves to let the smooth wave pass.
The production of the inductor is mainly manual, shielding. The assembly of the inductor depends on the fixture, otherwise, the tolerance will increase.
The resistance is usually easily overlooked because the Resistors is an energy-consuming component whose value does not have a large effect on the current, but with a large amount of heat loss, a lot of useless work is generated.
Some customers have requirements for resistance. In most cases, as long as there is not much difference, there is no big impact.
Generally speaking, it is easy to judge the quality of the Resistors by using a multimeter: adjust the multimeter to the appropriate gear of the electric barrier, and place the two test leads of the multimeter on both ends of the Resistors to read the Resistors from the multimeter.
Resistance value： It should be noted that the hand cannot touch the metal part of the test lead when testing the resistance.

What are the ways in which Modelsim works?

• Modelsim runs in the following four ways:
  1. User Graphical Interface (GUI) mode: The user interface of Modelsim is very friendly and is one of the main operation modes of the software, and the GUI mode directly inputs the operation command in the main window and executes it.
  2. Interactive command line (Cmd) mode: There is no graphical user interface, and all work is done only by commands entered through the command console.
  3. Tcl and macro (Macro) mode: The macro file with the extension of D0, or the Tcl grammar file can be executed, and the function equivalent to inputting commands one by one in the main window of GUl can be completed.
  4. Batch file (Batch) mode: Run the batch file under DOS, UNIX or LINUX operating system to complete the software function.

What are the characteristics of digital oscilloscopes and analog oscilloscopes?

An analog oscilloscope is an electronic measuring instrument that uses the characteristics of an electronic oscilloscope to convert an alternating electric signal that cannot be directly observed by the human eye into an image and display it on a fluorescent screen for measurement.

What are the structures and characteristics of several commonly used capacitors?

• Capacitors are commonly used electronic components in electronic equipment. The following is a brief introduction to the structure and characteristics of several commonly used capacitors for your reference.
  1. Aluminum electrolytic capacitor: It is made of an aluminum cylinder as the negative electrode, which is filled with liquid electrolyte, and inserted into a bent aluminum strip as the positive electrode. It also needs to be treated with DC voltage, and an oxide film is formed on the positive electrode sheet as a medium. Its characteristics are large capacity, but large leakage, poor stability, positive and negative polarity, suitable for power supply filtering or low-frequency circuits, when using, do not reverse the positive and negative poles.
  2. Tantalum-niobium electrolytic capacitor: It uses metal tantalum or niobium as the positive electrode, dilute sulfuric acid and other solutions as the negative electrode, and uses the oxide film formed on the surface of tantalum or niobium as the medium. Its characteristics are: small size, large capacity, stable performance and long life. High insulation resistance. It has good temperature performance and is used in equipment with higher requirements.
  3. Ceramic capacitors: use ceramics as the dielectric. The silver layer is sprayed on both sides of the ceramic substrate, and then the silver film is fired to make the electrode plate. Its characteristics are: small size, good heat resistance, low loss, high insulation resistance, but small capacity, suitable for high-frequency circuits. Ferroelectric ceramic capacitors have larger capacity, but larger loss and temperature coefficient, and are suitable for low-frequency circuits.
  4. Mica capacitor: Use metal foil or spray silver layer on mica sheet to make electrode plate. After the electrode plate and mica are laminated layer by layer, they are made by die-casting bakelite powder or sealing in epoxy resin. Its characteristics are: low dielectric loss and high insulation resistance. Small temperature coefficient, suitable for high frequency circuits.
  5. Film capacitors: The structure is the same as that of paper capacitors, and the medium is polyester or polystyrene. Polyester film capacitors have high dielectric constant, small size, large capacity and good stability, and are suitable for bypass capacitors. Polystyrene film capacitors have low dielectric loss, high insulation resistance, but large temperature coefficient, which can be used in high frequency circuits.
  6. Paper-based capacitors: Two pieces of metal foil are used as electrodes, which are sandwiched in extremely thin capacitor paper, rolled into a cylindrical or flat cylindrical core, and then sealed in a metal shell or insulating material shell. It is characterized by a smaller volume and a larger capacity. However, the inherent inductance and loss are relatively large, which is suitable for low-frequency circuits.
  7. Metallized paper capacitor: The structure is basically the same as that of the paper capacitor. It is a metal film on the capacitor paper to replace the metal foil. It is small in size and large in capacity. It is generally used in low-frequency circuits.
  8. Oil-immersed paper capacitor: It is a paper capacitor immersed in specially treated oil, which can enhance its withstand voltage. It is characterized by large capacitance, high voltage resistance, but large volume. In addition, in practical applications, firstly, different types of capacitors should be selected according to different purposes; secondly, the nominal capacity of the capacitor, allowable error, withstand voltage, leakage resistance and other technical parameters; thirdly, for positive, For negative electrolytic capacitors, the positive and negative electrodes should not be reversed during welding.

What are the evaluation indicators of the DTN routing protocol?

1. Message delivery rate. It is the ratio of the number of messages generated by the source node and successfully transmitted to the destination node in the simulation time to the number of all messages generated in the network, excluding the copies generated due to different relay and forwarding strategies during the routing and forwarding process. Maximizing the message delivery rate is the goal of DTN routing design, and the delivery rate is one of the most important evaluation indicators, which is closely related to practical applications.
2. Network load rate. is the ratio between the total number of messages that need to be delivered and the total number of messages sent.
3. Average delay. Indicates the time from the source node sending the data packet to the destination node receiving the data packet. The size of the delay will directly affect the availability range of the DTN, and the delay is also one of the important indicators that should be considered in the design of routing protocols.
4. Average hop count. The sum of the number of hops experienced by copies of all messages in the DTN network is compared to the number of all messages generated in the network. The average hop count reflects the overall performance of the routing protocol. The smaller the hop count, the more efficient the routing algorithm is. The number of routing hops is critical to the end-to-end delay.

What is the main lobe width in the pattern?

The pattern of the antenna consists of one or more lobes, and the lobes where the antenna radiates the strongest direction are called the main lobes.The main lobe width is the physical quantity that measures the sharpness of the antenna’s maximum radiation area.

What is a Java smart card?

The Java smart card is a CPU card based on the Java language.

What is the external photoelectric effect or photoelectron emission effect?

When the light is irradiated on the surface of some materials, if the photon energy of the incident light is large enough, the electrons of the material can escape from the surface and emit electrons outward. This phenomenon is called the external photoelectric effect or photoelectron emission effect.

What are the methods for powering the LEDs with the original power supply?

There are four cases: low voltage drive, transient voltage drive, high voltage drive and mains drive.

What are the characteristics of digital logic circuits?

Its characteristic is that the circuit processing speed requirement is relatively low, allowing a certain delay, but the processing scheduling is relatively complicated, and its main design method is CPU or DSP.

The core feature of the hard-core circuit is that the real-time requirements are high. The core feature of the soft-circuited circuit is that the scheduling is complicated.