We often see 0 ohm resistance in the circuit, for beginners, often very confused: since it is 0 Ohm resistance, that is the wire, why install it? Are there any resistors like this on the market? In fact, a resistance of 0 ohm is quite useful.
    Zero ohm resistance, also known as the jumper resistor, is a special purpose resistance, 0 ohm resistance is not the real resistance value of zero (that is what the superconductor does), because of the resistance value, it is the same as the conventional patch resistance error accuracy this indicator.

The following summarizes a series of uses of zero ohm resistance. 

    1. There is no function in the circuit, only on the PCB for debugging convenience or compatible design reasons.
    2. Can be used as a jumper, if a certain line is not used, directly do not attach the resistor can be (does not affect the appearance)
    3. When the matching circuit parameters are uncertain, replace them with 0 ohms. During actual debugging, determine the parameters and replace them with specific numerical components.
    4. When you want to measure the power consumption of a certain part of the circuit, you can remove the 0ohm resistance and connect the ammeter to facilitate the measurement of the current consumption.
    5. In the wiring, if the cloth can not pass, you can also add a 0 ohm resistance
    6. Act as inductor or capacitor under high frequency signal. (related to external circuit characteristics) inductance, mainly to solve EMC problems. As ground to ground, between power supply and IC Pin
    7. Single point grounding (The protection grounding, working grounding, and DC grounding are separated from each other on the device and become independent systems.)
    8. Fuse action
    9. Single point grounding of pseudo-ground and digital ground
    As long as it is the ground, it must eventually be connected together and then enter the earth. If it is not connected together, it is "floating", there is a pressure difference, and it is easy to accumulate charge and cause static electricity. The ground is the reference 0 potential, all voltages are derived from the reference ground, and the standard of the ground should be consistent, so all kinds of ground should be short-connected together. It was thought that the earth, which absorbs all electrical charges and remains stable, was the ultimate ground reference point. Although some boards are not connected to the ground, the power plant is connected to the ground, and the power supply on the board will eventually return to the power plant to the ground. If a large area of analog and digital land is directly connected, it will cause mutual interference. Not short and inappropriate, the reasons above there are four ways to solve this problem:
    (1) Connect with magnetic beads;
    (2) Connect with capacitors;
    (3) Connect with inductance;
    (4) Connect with 0 ohm resistance.
    The equivalent circuit of the magnetic bead is equivalent to a wave limiter with a resistance, which only has a significant suppression effect on the noise at a certain frequency, and the noise frequency needs to be estimated in advance when used in order to select the appropriate model. For situations where the frequency is uncertain or unpredictable, magnetic beads do not fit.
    The capacitor partition is directly alternating, resulting in floating ground.
    The inductor has large volume, many stray parameters and is unstable.
    The 0 ohm resistance is equivalent to a very narrow current path, which can effectively limit the loop current and suppress the noise. The resistance has a attenuation effect in all frequency bands (0 ohm resistance also has an impedance), which is stronger than the magnetic bead.
    The following two diagrams are a circuit, only because the component labels are different. R7 (R33) is a single point link between analog and digital.
    10. For current circuit when jumper
    When the electric ground plane is divided, the shortest return path of the signal is broken, at this time, the signal circuit has to detour, forming a large loop area, and the influence of electric and magnetic fields becomes stronger, which is easy to interfere/be interfered with. The 0 ohm resistance is crossed over the partition area to provide a shorter return path and reduce interference.
    11. Configure the circuit
    In general, jumpers and dip switches should not appear on the product. Sometimes the user will mess with the setting, easy to cause misunderstanding, in order to reduce maintenance costs, the application of 0 ohm resistance instead of jumper welding on the board.
The vacant jumper is equivalent to the antenna at high frequency, and the resistance effect is good with the patch.
    12. Other uses
    Wiring across the line;
    Debugging/testing;
    Temporarily replace other patch devices;
    As a temperature compensation device;
    More often it is the need for EMC countermeasures. In addition, the 0 ohm resistance is smaller than the parasitic inductance of the hole, and the hole will also affect the ground plane (because of the hole to be dug).
There is also a different size of 0 ohm resistance to allow through the current is different, generally 0603 1A, 0805 2A, so different currents will choose different sizes and reserve positions for magnetic beads, inductors, etc., according to the size of the magnetic beads, inductors also do packaging, so 0603, 0805 and other different sizes are available.