For the grounding of the electrical system, it is necessary to classify the grounding according to the requirements and purposes of the grounding. Different types of groundings cannot be connected simply and arbitrarily. Instead, they are divided into several independent grounding subsystems. Each subsystem has its common grounding point. Or grounding trunk, and finally connected together to implement total grounding. In addition to proper grounding design and installation, grounding of various signals must also be properly performed. There are roughly the following ground lines in the control system:
(1) Digital ground: Also called logical ground, it is the zero potential of various switching (digital) signals.
(2) Analog ground: Zero potential of various analog signals.
(3) Signal ground: usually the ground of the sensor.
(4) AC: AC power supply ground, which is usually the place where noise is generated.
(5) DC ground: DC power supply ground.
(6) Shielding ground: Also called chassis ground, it is designed to prevent electrostatic induction and magnetic field induction.
The above ground treatment is an important issue in system design, installation, and debugging. Here are some ideas on grounding:
(1) The control system should adopt a little grounding. Under normal circumstances, the high-frequency circuit should be grounded at the nearest multiple points, and the low-frequency circuit should be grounded at one point. In a low-frequency circuit, the inductance between the wiring and the components is not a big problem, but the loop formed by the grounding has a great influence on the interference. Therefore, one point is often used as a grounding point, but one point grounding is not suitable for a high frequency because the high frequency At this time, the inductance on the ground increases the impedance of the ground line, and inductive coupling occurs between the lines. Generally speaking, the frequency is below 1MHz, and one point can be grounded; when it is higher than 10MHz, multipoint grounding is used; between 1~10MHz, one point of grounding can be used, and multiple points of ground can also be used.
(2) Communication ground and signal ground cannot be shared. Since there are several mV or even several V voltages between two points of a power supply ground line, this is a very important disturbance for a low-level signal circuit, and therefore it must be isolated and prevented.
(3) Comparison of floating ground and ground. The floating of the whole system is the floating of each part of the system and the earth. This method is simple, but the insulation resistance of the whole system and the earth can not be less than 50MΩ. This method has a certain degree of anti-interference ability, but once the insulation is lowered, it will cause interference. Another method is to ground the chassis and leave the rest empty. This method has strong anti-interference ability, safety and reliability, but it is more complicated to implement.
(4) Simulation ground. The connection of analog grounds is very important. In order to improve the resistance to common-mode interference, shielding float technology can be used for analog signals. Grounding of specific analog signals must be designed strictly in accordance with the requirements of the operating manual.
(5) Shielding ground. In order to reduce the capacitive coupling noise in the signal, accurately detect and control in the control system, it is very necessary to adopt shielding measures to the signal. Depending on the purpose of shielding, the shielding ground connection is not the same. The electric field shielding solves the problem of distributed capacitance and generally connects with the earth. The electromagnetic field shielding mainly avoids the interference of high-frequency electromagnetic fields such as radar and radio. Made of high-conductivity, low-resistivity metal materials that can be connected to the earth. The magnetic field shielding is used to prevent magnetic induction of magnets, motors, transformers, coils, etc. The shielding method is to make the magnetic circuit closed with a high magnetic permeability material, generally it is better to connect the earth. When the signal circuit is grounded at one point, the shield of the low-frequency cable should also be grounded at one point. If there is more than one shield at the cable location, noise currents will be generated, creating a source of noise interference. When a circuit has an ungrounded signal source connected to a grounded amplifier in the system, the input shield should be connected to the amplifier's common. Conversely, when the grounded signal source is connected to an ungrounded amplifier in the system, the amplifier's input The end should also be connected to the public end of the source.
Information Organization: Yangzhou Tuopu Electric Technology Co., Ltd. Source:
Yangzhou Tuopu Electric Technology Co., Ltd. Address: No. 2, Guotai Road, Baoying County, Jiangsu Province, China Postcode: 225800
Telephone Mobile Fax Mailbox:
Website:
MDF Pvc door
MDF Pvc door, Door Wood Door Wooden Door Interior Glass Door PVC Door, China MDF Pvc door
ZHEJIANG HONGTUO INDUSTRIAL CO., LTD. , http://www.hongtuodoor.com