17

My only worry is the high frequency AC magnetic fields It's really all about a thing called skin depth: - Graph taken from this wiki page So, for example, at 100 kHz, copper has a skin depth of about 0.2 mm and this means a 1mm thick screen forms a fairly effective shield against magnetic fields leaking out or leaking in. I don't think that (even) 2 oz ...


16

That is a shield and is used for many purposes. It can be to protect a sensitive area from EMI/RFI, or it can be to protect the rest of the board from EMI/RFI generated in that area or to help pass emissions testing. If it is soldered down it can be problematic to remove as the large area acts as a heat sink preventing the solder form reflowing. Using a ...


16

This is what I do! Many, many excellent books have been written on the subject, but as a brief bullet-point list, focused particular on embedded systems for space usage: In general, we use many of the high-reliability design practices learned over many decades of hard-learned lessons from the defense, aviation and even automotive (brake controllers, ABS). ...


15

You would not be alone in this one. This is an often misunderstood phenomenon. Static magnetic fields can not be shielded. They can be re-directed using ferrous materials but even those will not block them. Electric fields on the other hand can be. Since an electric field is basically a voltage in space, they can not pass through a conductive plate that is ...


13

Solid would perform better, all other things being equal, but perhaps not significantly better. Since the 'holes' in your mesh will be a tiny fraction of a wavelength, the mesh should behave similarly to a thinner (higher resistivity) solid copper layer when measured from a relatively large distance away compared to the 'holes'. The 'shorted turns' you ...


10

One advantage of using shielded jacks is that the soldered shield tabs provide a very mechanically robust anchor to the PCB, reducing the chance of damage if the cable gets yanked.


9

You may or may not be over thinking this, it depends on what your application is, and if you have to pass any regulatory inspections for a product. The general idea is to shunt the ESD to ground through the chassis and away from your electronics. This depends on if your enclosure is insulated or not. Another thing to keep in mind is you can also have RF ...


9

Think of your PCB as parallel plate waveguide, with the top and bottom ground planes acting as parallel plates. Now, since you want waves neither exiting nor entering this waveguide, you'd try to build a "wall" around them – or more, a fence, which the small vias around the edge do. The fact that the ground plane is exposed around the corners (i.e. no ...


8

There does not need to be a shield. Standard ethernet cable has no shield, so even if the socket were shielded it wouldn't do much for the data on the cable. I think the reason there are shielded RJ-45 jacks is so that you can make a reasonably tight chassis without a gap in it at the connector, but that is just speculation on my part. The way to deal ...


8

I think I've only seen drain wires in foil-shielded cables (but I could be wrong...). It is not possible to make a secure connection to the foil shield, so the drain wire is the only way to make the shield connection. A drain wire is not required with a braid shield, as you can unbraid a bit of the shield, and twist the strands to make a "wire" that you ...


8

The wire has inductance and, the longer the wire is the more inductance it has. An inductance likes to maintain the current flowing through itself so, when your switch opens, the small stored energy in the cables magnetic field tries to maintain current flow and produces a sizable voltage (aka back-emf) in doing so. This can easily exceed the maximum voltage ...


7

The LVDS are differentially terminated (across phases) so there should be no net flow of current - it is balanced. The twisted pairs give you quasi TEM mode propagation so the concern of the shield here is purely electric field. terminate at one end as you have drawn to avoid introducing current loops. Since you have implemented a differential CAN system ...


7

If you have a balanced audio signal (e.g. XLR), then the idea behind a twisted pair is any interference that one wire picks up will also be captured by the other wire. The device that receives the signal only cares about the difference between the two levels, so any common mode noise can be ignored. This is extremely important for long runs (lots of ...


6

First note that you are messing with systems directly related to the control of your vehicle's airbags - a safety critical system that can really hurt you or kill you: If you need it to work and it doesn't, and If you expect it to not work and it does Work on this system at your own risk. The Weight Sensor Control Module provides amplification and ...


6

The cable connector body must contact the chassis connector body, which is generally metal, conductive, and bolted to a conductive metal case. Therefore the only choice for the connector body is a connection to the equipment case. This (the equipment case) is obviously grounded - to safety earth. There is no choice about this. However it is common for ...


6

Acting as a faraday cage, an ungrounded shield covering a twisted-pair will be somewhat effective. When in the presense of an interfering electric field, both wires in the twisted-pair are influenced more similarly than without the ungrounded shield and, this means that if the input stage that receives the signal has a decent common mode rejection figure, ...


6

I worked for a company that put ground layers at top and bottom and stitched them together all round the board perimeter, trying to make a Faraday cage. The product still radiated a lot. Turned out to be the 68000 chip die was radiating through the plastic package which was picked up by the adjacent power cord and emitted from there. I think EMC follows ...


6

A shield usually makes a pretty good protector against electric field disturbances (half the story) but, unfortunately, makes a pretty poor protection against magnetically coupled noise (the other half of the story). Twisting the conductors in a pair mainly ensures that induced voltages (due to external magnetic disturbances) are equalized on both ...


5

Yes, it sounds like (a little confusing) you have a ground loop problem, and yes they can matter, especially when trying to measure small analog signals. If all grounds tie back to the same outlet strip via relatively short line cords, then it would probably be OK. However, you say that this cryostat thing (whatever that is) is connected separately to ...


5

A piece of metal foil (any metal) adjacent (within a few mm) to the card will do it. It does NOT need to be wrapped round the card - close to the card on one side, and at least about a quarter of the area of the card will do fine as this will damp any read field. As the card is powered from the read field, you do not need to absorb anything like the same ...


5

A drain wire is normally there to compliment a foil shield. The foil is actually bonded to a very thin film of plastic and stretching of this plastic could cause the foil to break, thus breaking the path to ground. The drain wire ensures that the foil always has a reliable path to ground throughout the length of the cable. In addition, you cant solder ...


5

Existing answers are correct. It may be worth also noting that I've heard them referred to colloquially as "cans".


5

These shields are used to deaden EMI/RFI both to the circuit, and from the circuit. I have seen them most often used to contain RF noise so that the product passes regulatory emissions testing. Also, these can help "modularize" the design. One of the problems with RF circuitry is that the tuning changes with the surroundings. Generally an RF-enabled ...


5

You didn't provide this information, so I am assuming your DAQ has differential inputs. If you have a sensor with a differential output, you may not want to load the two lines of the differential output differently - so they should go in a shielded twisted pair or two coaxes to maintain balance. Also, often you may not be able to connect one of those signals ...


5

In the United States the FCC (Federal Communications Commission) Part 15 regulates unlicensed transmissions. It doesn't matter whether you are using a "module", it is the unlicensed use of any transmission. The FCC doesn't care HOW you comply with the regulations. If a device complies with regulations without using a shield, so much the better. ...


5

Connect your shield pins to GND, then run a grounding wire/strap from your metal enclosure to something else in the vehicle that's grounded so you'll have somewhere to "dump" noise. In most vehicles just about every metal surface is grounded to the (-) terminal of the battery (unless you have a wonky + ground vehicle). You can pull ground from a radio gnd ...


5

There are two approaches to this problem that make sense: Connect the chassis ground and the signal ground to the chassis at many points, but do not connect them to each other Connect the chassis ground to the chassis, and leave the other mounting holes isolated, then connect the chassis ground to the signal ground at where the signals cross the plane split....


5

This product might as well be filled with fu-fu dust for all the good it will do. The website provides no details of operation or specific ranges covered. It looks like a cheap watch you could buy anywhere for $10 USD. There are devices called 'jammers' that make broad-band noise that can include audio 'pings' as well as RF sweeps, but these toys cost ...


5

I'll assume your jack is a stereo one, like on this picture: Cable shield goes to ground (see pic) and left/right signal wires go to the two smaller lugs.


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