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Questions tagged [shielding]

Questions regarding shielding devices against noise, interference, or ESD. Not to be confused with arduino-shield.

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53
votes
12answers
64k views

How to connect USB Connector shield?

How should I route USB Connector shield on PCB? Should it be connected to GND plane right where USB is placed, or should the shield be isolated from GND, or should it be connected to ground through ...
31
votes
3answers
4k views

Correct place to attach shields for twisted pairs

I have two PCBs connected by a cable containing 5 sub-cables: 6v power through a custom made coaxial cable (similar to that found on laptop power supplies). 2x 100mbps LVDS through 100ohm impedance ...
29
votes
6answers
12k views

Noise reduction strategies in electrophysiology

When recording electrical signals from cells (in a dish or inside a living human or animal body), one major problem is to increase the signal to noise ratio. These signals are usually in the 10uV ...
19
votes
1answer
2k views

Shielding can, what is the proper way?

I like to protect a sensitive circuit of mine with a shield. I don't have a picture but basically, I have put together a 1 mm thick ground rectangle on the top layer, and I will place the shield ...
15
votes
2answers
2k views

Grounding PCB to enclosure

I am designing a small sensor which fits into a custom aluminum enclosure. The sensor uses CAN bus and a long cable to connect it to the host and power. The shield of the cable will ground the ...
13
votes
3answers
2k views

Does Shielding “Electrically” shield “Magnetically” too?

I know it sounds like a newbie question but I can't wrap my mind around it. An electromagnetic field is electric + magnetic field. So this means that when shielding an equipment offensively, for ...
13
votes
3answers
7k views

How to Connect USB/Ethernet Shields to Chassis or Digital Grounds

I have a PCB with a few USB and RJ-45 Ethernet connectors on one side. I'm quite confused as to how exactly I'm supposed to be hooking up the SHIELD pins on them though. This is for a host device ...
11
votes
3answers
2k views

What is a more effective shield for magnetic fields between 300 and 500kHz Solid copper or copper mesh?

I am working on a PCB that is very crowded, and has high gain amplifiers working between 300kHz and 500kHz Typically I would use Mu metal or similar for shielding at this frequency, but obviously ...
11
votes
2answers
2k views

Can a shield propagate EMI?

At a job site we typically have 10 vehicles connected to a single vehicle (star layout) by a 100m 5 conductor cable carrying power(unused), ground, shield, CANH, and CANL. The shield is grounded on ...
11
votes
2answers
905 views

Purpose of bare copper perimiters on HF PCBs

I have seen many RF PCBs with a thick, rounded area of exposed copper going all around the PCB, like in this example: My intuitive thought is that this is for some kind of grounding or shielding can, ...
10
votes
3answers
2k views

Shielding and Ground loops

I have various pieces of equipment that all need to be connected to GND (Chassis GND). The issue I'm having is that I'm connecting an ADC card inside a computer through a metal box with custom ...
10
votes
1answer
3k views

USB 3.0 Hub shield connection

This is about the seemingly controversial shield to ground connection. The system is basically a body-worn intel-based computer, powered by a battery. Two USB 3.0 (or 3.1 Gen1) cables come out to a ...
9
votes
3answers
22k views

How important is the shield on an RJ45 connector?

If I am going to use a PCB mount RJ45 connector for 100mbps Ethernet, does it need to be a shielded connector, or can I get away with using an unshielded one? Is there some standard which deals with ...
9
votes
7answers
7k views

Why does an XLR connector use 3 pins instead of two

Why does XLR connectors use 3 pins instead of just 2. The wiring is Pin Function -------------------------------- 1 Chassis ground(cable shield) 2 hot 3 cold ...
9
votes
2answers
2k views

How to check whether a component can work in strong magnetic fields?

I want to design my PCB to operate nicely even when we place it next to a neodymium magnet. How to check whether my component can work in such condition without shielding? Edit: I haven't face any ...
8
votes
2answers
1k views

Design Considerations for Electronics in Space [closed]

What additional constraints do we face when designing electronics/microsystems for use in orbit? What kinds of shielding techniques are employed? Is it common to enclose all electronics in a faraday ...
8
votes
3answers
1k views

Why does my GPS and Wi-Fi work inside a sealed copper clad box?

I have just finished assembling a Raspberry Pi-based project into a DIY box made from copper clad FR4 PCB, with the edges soldered together and the copper surface connected to ground. I expected, ...
8
votes
1answer
2k views

Does an ungrounded shielded cable shield at all?

Does a shielded cable provide any shielding if the shield isn't grounded? Would it be practically different than an unshielded cable?
8
votes
1answer
2k views

Proper shielding techniques for chassis grounded equipment located 30 feet apart

I am just hoping to get some best practices out of this discussion: I have two pieces of equipment that are located about 30 feet apart and bolted to a metal frame (chassis ground). They interface ...
6
votes
3answers
229 views

Wire to use with Sensors

I am trying to minimize interference in a sensor project. Can anyone recommend a good shielded wire I can solder into my board?
6
votes
1answer
1k views

Running network cable near X-Ray equipment

My mother runs a small veterinary clinic. She is getting a new X-Ray machine that will need a network connection to send digital copies of the X-Ray to the server. I will be installing a wall plate ...
6
votes
2answers
2k views

Aluminum project box: should BNC conenctors touch it?

I want to make a aluminum shield box (this is my first time!), I made some holes to host some female BNC connectors. Now my question is, should I isolate the BNC connectors from the box? Or should the ...
6
votes
6answers
1k views

Shielding Techniques for Digital Sensor

What shielding techniques would be best suited for a digital sensor (3 wires - Pwr, Gnd, Sig) in a noisy environment (specifically fluorescent lighting)? Twisted pair (trio in this case) works well ...
6
votes
1answer
6k views

How do I shield my pc-speakers from mobile interference? [closed]

I have a budget (not cheap :P) pc-speaker set from Logitech (2.1) at home which are extremely sensitive to cellsignal interference. My iPhone is about 1m from any part of the set - including the ...
6
votes
2answers
2k views

Why does a radio still work inside a metal box?

I've put a small battery powered commercial radio inside a Quality Street tin. The tin is all metal with rolled joints and the lid is a tight fit. I'd be willing to bet that there are no holes ...
6
votes
2answers
2k views

How can I make a diy anechoic chamber?

I'd like to make a small anechoic box for RF measurements. I need roughly a 30x30x30cm cube of usable space, and I'd like the reflections from the walls to be attenuated by 10dB or more from 100MHz ...
6
votes
2answers
2k views

Faraday cage mathematics

We all know the Faraday cage effect: light waves get through the screen on the front of your microwave oven, because their wavelength is much less than the size of the holes, whereas the microwaves ...
6
votes
2answers
1k views

How is this crystal / ferrite bead / ground shield connected?

This is part of the schematic for a TI TAS1020B USB Streaming Controller MCU that I don't quite understand. Obviously the shield connects to one end of the ferrite bead, but what else? Are the XTAL ...
5
votes
5answers
4k views

What are these metal plates covering parts of PCBs called?

I am trying to fix my wireless router, but one of the parts is under a metal plate. What are these metal plates called? This is what it looks like when it is removed: (The gold coloured plating ...
5
votes
2answers
2k views

Coaxial cable vs shielded pair

I need to wire a sensor with analog output to an acquisition system, and the presence of a separate "shield" connection on the DAQ made me thinking: why would I use a shielded 2-wire cable versus a ...
5
votes
3answers
5k views

Non-metal cases

This question is really aimed at computer cases, but I suppose it also applies to other PCB cases. Most of the Computer cases I come across are aluminium, or else some other metal; As I understand it ...
5
votes
3answers
168 views

Running router out of its case

I'm currently building a robot, and as part of its spec it must connect to a wifi network. I have a Belkin wireless router, which I have taken out of its case to expose the PCB. My question is: Is ...
5
votes
2answers
971 views

Ethernet shielding termination

With regard to termination of ethernet shielding I have been taught always to terminate only ONE end of the shielding to ground to prevent ground loops occurring. Is this best practice? and is there ...
5
votes
2answers
996 views

Confusion in grounding shield wires of transducers

There is a 6-wire Wheatstone bridge type load-cell and one of the wire is called shield and it is electrically connected to the metallic case of the load cell as below(I marked that with yellow ...
4
votes
5answers
13k views

How do I shield a card like Visa payWave and MasterCard PayPass to block its communication?

This is basically a replication of this question on Personal Finance SE. Suppose there's a wireless smart card like Visa payWave or MasterCard PayPass or MIFARE Ultralight. The owner wants to ...
4
votes
5answers
6k views

Shielded vs Twisted cables

For some reason low voltage, high quality audio interconnects seem to be made of 3 wires braided together, when normal low voltage audio wires are two wires surrounded by a grounding sleeve. I'm a ...
4
votes
2answers
1k views

Long wires causing Raspberry Pi to die?

I've been working on a simple project involving a Raspberry pi and some switches. I would never thought I would have any problem for something as simple as a switch, but here I am. The 2 wires from ...
4
votes
1answer
2k views

What is the effect on noise immunity of a floating shield on a shielded twisted pair

We have an installed system where resistive sensors are connected to some electronics by shielded cables of between 2 and 10 metres. The cable is a twisted pair sheathed in a stainless steel braid. ...
4
votes
2answers
5k views

EMI/RFI emissions and computer cases

I have designed a computer case (enclosure) for mini-itx motherboards. Its bottom and rear are made out of 2mm thick aluminium and the sides and top out of 4mm plastic (ABS). I'd like some advice ...
4
votes
1answer
922 views

Best practice design ground and shielding

Case: I design a pcb with a microprocessor and a adc (I'll leave out the details). Is this correct: The digital ground and the analog ground should be connected, but by a small passage. Next ...
4
votes
1answer
1k views

Making aluminium conductive for an RF shield enclosure

I'm not sure if it's appropriate to ask here, but I would assume many people in electronics would have experience with this. I'm enclosing an RF sensitive PCB into an sealed aluminium enclosure. ...
4
votes
2answers
967 views

eliminate noise pickup from shielded enclosure's surface

I have a test instrument that measure spectral energy density versus frequency. The measurement is extremely low noise. The RF input on the test instrument is an SMA-connector where the inner ...
4
votes
1answer
619 views

Shielded cable vs. unshielded in underwater environment

I know basic electromagnetic theory very well and understand why this works but I'm not sure about one thing regarding usage of coaxial (shielded) cable vs. unshielded (normal conductor) cable when ...
4
votes
4answers
262 views

Energized circuit in a 3M Static Shielding Bag (silver color)

I'm wondering if it's safe to put an energized circuit in a static shielding bag...as part of a high altitude balloon project. I'm not too sure how these work, so I tried seeing if either the outside ...
4
votes
1answer
4k views

How can a shield winding in the transformer be helpful without fully covering the core?

This article describes the Apple iPhone charger circuitry in great details. It mentions the shield winding in the flyback transformer. The shield winding is simply an extra most outer winding and the ...
4
votes
1answer
1k views

DVI Shield pins

Should I connect the Shield pins 3, 11, 19, and 22 on my DVI connector to GND on my PCB? What consequences might I expect if I leave the shield pins floating?
4
votes
2answers
733 views

What types of Shielding and Filtering would allow devices to be used in a MRI environment?

I'm working on a respiration monitor and I was wondering what area of electronics I would need to get familiar with to design the hardware filters that would stop the RF/EMI from frying the system. ...
4
votes
2answers
81 views

Why is shielding effectiveness different for various hole geometries?

I have run into the equation below in various literature/app notes. (example). I have never seen the derivation for such an equation and don't understand why round apertures are more effective at ...
4
votes
3answers
2k views

What properties of metal makes make them suitable as EMF shielding material?

What properties of metals make them effective at shielding against EMF, and which metals are typically used? How does Aluminium, Steel, Copper and Lead compare?
4
votes
2answers
202 views

Thickness of low frequency Mu shield calculation

I am dealing with a low frequency varying magnetic field, say 10 - 100Hz with a magnitude of 0.8T. It seems shielding at this frequency gets tricky. Even though Mu is capable of doing it, there should ...