As long as it is the ground, it must be connected together, and then into the earth. If they are not connected together, it is "floating", there is a pressure difference, and it is easy to accumulate charges and cause static electricity. The ground is referenced to the 0 potential, and all voltages are derived from the reference ground. The ground standards must be consistent, so various grounds should be short-circuited together. It is believed that the earth can absorb all electric charges and always maintain stability. Although some boards are not connected to the earth, the power plant is connected to the earth, and the power on the board will return to the power plant to the ground. If the analog ground and the digital ground are directly connected in a large area, it will cause mutual interference. There are four ways to solve this problem if it is not short-circuited or appropriate. There are four ways to solve this problem: 1. Connect with a magnetic bead; 2. Connect with a capacitor; 3. Connect with an inductance; 4. Connect with a 0 ohm resistor.

The equivalent circuit of the magnetic bead is equivalent to a band-stop wave limiter, which can only significantly suppress the noise at a certain frequency point. The noise frequency needs to be estimated in advance in order to select the appropriate model. For situations where the frequency is uncertain or unpredictable, the magnetic beads do not match; the capacitors are separated from each other and cause floating; the inductance is large, and there are many stray parameters, and it is unstable; 0 ohm resistance is equivalent to a very narrow current path, which can effectively limit Loop current makes noise suppressed. Resistance has an attenuation effect in all frequency bands (0 ohm resistance also has impedance), which is stronger than magnetic beads.