Confusion between shield and chassis of a connector - Page 1
Forum section: electronics / beginners

author: Freshman
author_rank: Regular Contributor
timestamp: March 05, 2024, 06:06:21 am
content: I am new to Ethernet and working on it.When selecting a connector and designing it, I have some confusion with the terminologies.This is the connector:https://www.digikey.in/en/products/detail/molex/0438600004/410218?cur=INR&lang=en&utm_adgroup=&utm_source=google&utm_medium=cpc&utm_campaign=PMax%20Shopping_Product_High%20ROAS&utm_term=&productid=410218&utm_content=&utm_id=go_cmp-20122528480_adg-_ad-__dev-c_ext-_prd-410218_sig-CjwKCAiA_5WvBhBAEiwAZtCU7_GzftXryWo8Xap_FUBWtzU-yLtLikAacuD0M6AImZf_b5NfmIuHkhoC5iMQAvD_BwE&gad_source=1&gclid=CjwKCAiA_5WvBhBAEiwAZtCU7_GzftXryWo8Xap_FUBWtzU-yLtLikAacuD0M6AImZf_b5NfmIuHkhoC5iMQAvD_BwEMy questions are:1. Which parts in the connector is called the shield and which is called the chassis?2. What are the two finger pointed/present at the top of the RJ45 connector?From my understanding from having read multiple articles:I guess that shield and chassis terms refer to the same outer casing of the RJ45 connector. When a CAT 8p8c cable is connected, the drain wire of the cable is connected to the chassis/shield portion of the connector.Is my understanding correct?I have watched this video:One thing I am still not able to find is that,1. Since the 8p8c wires, in the ethernet cable, are all differential, they are referenced to each other, why is there a need for the drain wire alongside (within) the ethernet cable?2. Where is the other end of the drain wire connected to?3. From the video: What does signal ground mean? - Does he mean the drain wire?4. Does earth ground imply the chassis/shield of the connector?Getting some confusion on this topic.It would be very helpful if someone can clarify with some images on the drain wire/Signal ground/earth ground questions as I have searched many places and couldn't get clarification on this topic.Thank you.

author: Solder_Junkie
author_rank: Frequent Contributor
timestamp: March 05, 2024, 10:58:24 am
content: The shield of a Cat6A cable goes to the metal shield of the plug. The sockets have a metal body that connects to the chassis of the equipment, or the ground area of a printed circuit board.This provides shielding from one piece of equipment to another, as if their cases/chassis were touching each other.See this pdf showing how to make the RJ45 connections for Cat6A shielded cables.https://docs.rs-online.com/359b/0900766b816e835a.pdfSJ

author: selcuk
author_rank: Frequent Contributor
timestamp: March 05, 2024, 01:04:57 pm
content: These ground-chassis-shield topics are a little complicated to explain here shortly. I will get confused if I try to. I suggest you to read a textbook about them. If you don't have one, below link is an open access one. It has full chapters for shielding and grounding.Design for Electromagnetic Compatibility--In a Nutshell Theory and Practice (Reto B. Keller)

author: Jwillis
author_rank: Super Contributor
timestamp: March 05, 2024, 09:58:43 pm
content: Different grounds can have different potentials relative to each other. Earth ground is considered to be a truly 0V reference whereas other grounds like chassis and circuit grounds can be aloud to float (be a higher potential) above earth ground and circuit grounds can float above chassis grounds. So by tying shielding for the circuit to chassis ground and/or Earth ground theirs a potential difference. Current flows from the highest potential to the lowest potential. So currents induced either by the circuit or from external sources will flow through the shielding to the lowest potential instead of the circuit. Potential differences don't need to be much to cause problems in sensitive circuits or between two separate circuits. The metal shield for example on an Ethernet connection is there if the cable provided with metal connector and shielding also. This puts the cable shielding and the device shielding to the same potential minimizing EMI radiating from or to the circuit. In most cases the lack of shielding on a cable doesn't pose much of a problem but can become a problem with many bundles. Un-shielded bundles can induce cross talk which causes errors which slows the system down because of the constant re communication to correct those errors in the signal.