Do you connect the instrument cable Earth wire to both side?
When it comes to connecting the Earth wire of an instrument cable, it’s important to consider the specific requirements of the system you’re working with. Generally, the Earth wire, or ground wire, is used to protect against electrical interference and safety hazards.
For instrumentation earthing, there are typically three types of earthing systems:
- Safety Earth (SE): Also known as Dirty Earth, Protective Earth, Electrical Earth, or Power Earth.
- Instrument Earth (IE): Also referred to as Electronic Earth, Reference Earth, Clean Earth, or Signal Earth.
- Intrinsic Safety (IS) Earth: Required only for IS circuits with IS instruments1.
The Instrument Earth is primarily aimed at providing a low impedance path for noise currents induced by RFI/EMI, which may affect analog signals. The shields of single or multi-pair analog instrument signal cables are connected to this earth1.
As for the question of whether to connect the Earth wire to both sides, it depends on the type of cable and the equipment you’re using. For shielded cables, some sources recommend grounding the shield at one end only to avoid ground loops, while others suggest grounding at both ends to prevent RFI problems2. It’s crucial to ensure that there is isolation between each type of earthing to fulfill their intended purposes1.
In summary, the connection of the Earth wire can vary based on the type of earthing system and the specific requirements of the equipment. It’s always best to follow the manufacturer’s guidelines or consult with a professional electrician or engineer to determine the most appropriate method for your situation. In process industries, the practice regarding the connection of the instrument cable Earth wire can vary based on several factors, including safety regulations, industry standards, and specific project requirements. Generally, the Earth wire, also known as the ground wire, is connected to provide a safe path for electrical currents to discharge in case of a fault or surge, thus preventing electrical hazards.
In many cases, the Earth wire is connected at both ends of the instrument cable to ensure proper grounding and safety. This connection helps to maintain electrical continuity and provides protection against potential electrical faults or interference. However, there might be situations where specific design considerations or local regulations dictate otherwise.
It’s essential to adhere to relevant codes, standards, and guidelines established by regulatory bodies such as the National Electrical Code (NEC) in the United States or the International Electrotechnical Commission (IEC) for international projects. Additionally, consulting with electrical engineers or experts in the field can provide further guidance on the appropriate grounding practices for instrument cables in process industries.