Dear all:
My company is located in China. In our company, for each piece of equipment, in addition to requiring electrical grounding, an extra static grounding connection is also necessary. In this background, I have some doubts regarding the grounding requirements in ESD S20.20. I hope that all experts can help me understand them. . Firstly, what does the grounding conductor of the equipment refer to? The standard requires it to be less than 1 ohm. So, how exactly should one measure it using a multimeter? The second question: I understand that the auxiliary grounding refers to the resistance value between the electrical ground and the static ground. Is this understanding correct? If it’s incorrect, could you provide an example of common auxiliary grounding found in the EPA?
Sameer,
The equipment grounding conductor in ANSI/ESD S20.20 refers to the ground that factory equipment is typically grounded to. In European standards it is referred to as protective earth. If your factory is using this as its means for a grounding/bonding system, then the requirement is < 1.0 ohm impedance, although this measurement is not required if the factory has ground fault circuit interrupters (GFCIs) installed. The impedance is typically measured by using a circuit tester connected to a grounded outlet.
It appears you are using a separate static grounding system, which I have heard is required in China. If this is true, then that could be considered an auxiliary grounding/bonding system. The requirement is the auxiliary ground should be < 25 ohms to the equipment grounding conductor. This could be measured using a multimeter between a static grounding point and an equipment grounding connection point.
Auxiliary grounding/bonding systems are typically found where an organization wants a separate grounding system to connect parts to ground for reasons other than safety. In European standards it is referred to as functional ground.