Why chassis ground

Chassis grounding serves the same purpose for electronics as lightning protection does for high voltage power systems. Specifically, to route unwanted and potentially dangerous current away from the system elements and components to prevent circuit operation interruption and damage. In these cases, metallic chassis effectively serve as earth ground in that they terminate the physical circuit path for unwanted currents. This coupled with usage for EMI minimization illustrates how important chassis ground can be for your electronics systems.

However, good grounding techniques; as listed below, must be implemented for chassis grounding to be most effective. There should be a single ground connection from each PCBA. For multiple boards, all ground connections should be connected to a single point. For large electronic systems, each internal system should have a single ground connection where all internal board grounds connect.

Whether using the enclosure or mains neutral as the chassis ground, there should be a single connection to the electronic system s for which it serves as the safety ground. For electronic systems within structures, a path to earth ground is available and should always be used.

For portable electronics that contain their own power supply, consider the power supply return as the earth ground and use a single connection from the internal circuits for grounding.

As with most safety measures, the importance of chassis grounding can be overlooked until a contingency occurs and your board or system is fried or worse someone is injured.

These can be avoided by recognizing how critical chassis grounding techniques are and implementing them during design. At Tempo Automation , we not only build your boards faster than anyone in the industry but are experienced in PCBA safety and quality and will assist you to ensure your boards are developed to reliably meet their operational objectives. And to help you get started on the best path, we furnish information for your DFM checks and enable you to easily view and download DRC files.

In theory, a ground is an electrically-neutral point. Like signal traces, ground planes have impedance and when measured they will be at small voltage levels. While the non-zero voltage of ground rarely causes trouble, chassis grounding is still important, as ground planes are susceptible to transient events that cause a sudden surge in current. There needs to be a safe channel for excess current to flow or it will cause damage to the components. The chassis ground is a safe and effective path to divert that excess current.

Ground is portrayed as a stable reference plane for electronics signals but realistically, it is anything but. All signals need a return path and the ground plane serves as one. A signal ground plane that becomes the return path of a digital signal is considerably noisy. Chassis grounding is an important part of the ground separation strategy to reduce ground noise.

It provides a dedicated return path for the ground current to earth ground. Chassis grounding not only helps in protecting the PCB from surges and ground noise, but it may also act as a shield against EMI. A grounded, enclosed chassis can be an effective Faraday cage, which protects the PCB from external interference. Chassis grounding can be tricky. Here are a few strategies to keep in mind:. Note that the analog circuit has separate ground designations from the digital and that there is one defined connection between the two.

Normally this connection would be as close as possible to the power supply common. Voltage measurement examples Voltage measurements relative to circuit ground.

A virtual ground can be created using an op-amp. C1 stabilises the reference voltage and keeps it constant during fluctuations in V CC. U1 provides the virtual ground. C2 is the supply decoupling capacitor for the op-amp. See also Opto-triacs, solid-state relays SSR , zero-cross and how they work.

Now to calculate the cable size you have to take in the length of the return negative cable as well. Using the example requirements above with a twin cable installation i. I'm not an electrical engineer, but it seems to me if the chassis is indeed a suitable ground whether or not the negative side of the battery is connected , then the usual explanation of why we should always disconnect the NEGATIVE terminal prior to working on our car is bogus see link below.

As long as the positive cable is connected, we run the risk of shorting out any number of circuits in the system. I've blown enough fuses to learn the hard way. Disconnecting the Power Supply. Since the spark plug has only one port for positive the negative comes from the engine block. Grouding engine block means grounding chassis. Long time ago when I was wiring up a cart that we built decided to wire up all the grounds directly to the battery that way I foolishly thought i would not have to ground the chassis.

You know when you just want to do something for no good reason. Yeah but the engine wouldn't spark and after breaking my head over it I realized that it needed ground. Soon as I put a jumper cables from the negative terminal to the engine block she fired up.

I think manufacturers could easily come up with 2 ports on a spark plug today but there's no use for that. Chassis ground also help greatly in reducing electrical spikes caused by ignition coils. There are already very good answers already posted. However, I want to show my point. Using car chassis as GND is a very good design choice, When you're working on a repair or any modification, if we just disconnected the GND from mains, it's quite safe from shorts and fire, which may accidentally happen due to unintended short while working with metal parts.

Instead of disconnecting each cable separately. Another benefit is when you want to do some modification on the electrical part, like adding a led strip, separate tail light, etc. It's like pulling neutral from the neutral bus bar, rather than going to the main wiring for adding new components in a room.

To have a additional security level: If any cable connections gets lose, falls onto the chassis and sets it under voltage a current would flow through the body of some one touching it. This is a high risk to people. To avoid this it get set to ground.

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