Practical grounding, bonding, shielding and surge protection. Usb hardware design guidelines for ftdi ics ftdi chip. This is the layer where various cable types differ most. I think those recommending resistors, or not connecting. Ralph morrison, president of instrum and the author of grounding and shielding techniques in instrumentation published by wiley. Techniques for measuring shielding effectiveness will be addressed. It also provide personal safety and protect the equipment. This is a discussion of the basic principles behind grounding systems and how grounding is related to safety and the effective operation of circuit protection devices such as fuses and circuit breakers.
More power flowing through the aircraft means higher levels of electromagnetic interference emi. The practice showed, that the biggest problem is to find quality usb cable. Connect the shield at the source switch end of the cable only. Disclaimer this document is provided as is with no warranties whatsoever, including any warranty of merchantability, fitness for any particular purpose, or any warranty otherwise arising out of proposal, specification, or sample. Understanding shielded cable page 3 a third approach, seen in alpha wires suprashield products, combines both foil and braid shields in protecting the cable. The examples discussed show that singlepoint grounding of control cable shields protects the central cores from capacitive inphase relative to earth interference only, while grounding at both ends will ensure protection of the central cores from any type of interference.
Schematic of a perfectly bonded penetrable shield when a good shield is connected imperfectly, such as in the case of a pigtail connection, there is an impedance in. Cable shield grounding assembly installation instructions attention. Practical grounding, bonding, shielding and surge protection unlike many books on grounding and shielding, provides straightforward, practical solutions to commonly encountered realworld situations and enables one to better understand proper ground methods and to quickly recognize and solve existing grounding issues in a facility. The net result of these instructions, is to isolate the pcb ground plane from the usb shield. They help reorient a person to the hereandnow and in reality. Grounding and shielding techniques wiley ieee kindle edition by morrison, ralph. Grounding and shielding this article was written for calex by mr. Grounding is a technique that helps keep someone in the present. This grounding and shielding diagram will reflect the special requirements of sensitive equipment experiments, sensors, considers the geometrical box configuration of the system shows harness routing, cable shielding, shield grounding, interface circuitry, cable. Since 1994, he has helped thousands unravel the mysteries of grounding and signal. You should always have a connection to earth ground, for personnel safety.
Jun 25, 2018 the multitude of app notes and articles on this subject that recommend grounding the shield at one end only misrepresent the physics of shielding and falsely ascribe a ground loop to the shield where the circuit itself was part of the original ground loop. Medium and highvoltage power cables, in circuits over 2000 volts, usually have a shield layer of copper or aluminum tape or conducting polymer. Grounding and shielding of amplifier, bridgesensor and voltsensor input leads noise can couple into lowlevel signals in a variety of ways. Grounding is a set of simple strategies to detach from emotional pain for example, drug cravings, selfharm impulses, anger, sadness. When sending full speed signaling, usb cables rely on the shielding integrity of the. Practical grounding, bonding, shielding and surge protection practical professional books g vijayaraghavan, mark brown, malcolm barnes on.
Grounding skills can be helpful in managing overhelming feelings or intense anxiety. The usb universal serial bus specification defines the mechanical and. Proper grounding techniques of shielded ethernet cable. There are two types of shielding typically used for cables. Use filtering on those lines, such as power and ground, that cannot be kept clean. The grounds for emc design 2 grounding in emc engineering grounding is probably of electricalelectronic system design, often considered as black magic not easy to understand intuitively no straightforward definition, modeling or analysis many uncontrolled factors affect its performance.
Distraction works by focusing outward on the external worldrather than inward toward the self. Cable shield grounded at one end only emc standards. The correct place to connect an electrostatic shield is at the reference potential of the circuitry contained within the shield. Power, grounding, bonding, and audio for ham radio safety. Bureau of industrial security bis export administration regulations ear and requirements. Grounding demystified 3 2 categories of solutions applied for compliance. This note summarizes the proper techniques and is intended as a. Effectiveness of shield termination techniques tested with tem cell and bulk current injection arthur t.
The integrity of both the facility grounding and the proper equipment operation depends on the proper bonding of the grounding electrode system, proper system grounding of service equipment and. If you have a metal enclosure, this will be your shield ground. Bonding the usb cable shield to gnd on both ends is the best only way to deal with that. The angelus corporation is committed to complying with all united states export laws and regulations. It was working fine, but i noticed an annoying hum that went away if i touched pretty much anything metal on the guitarthe strings, tuners, or the frame around the jack. A shielded cable is an electrical cable of one or more insulated conductors enclosed by a common conductive layer. Usb device cable shield connection grounding it or not. Prior to pulling the cable through the stuffing tube, remove and discard the gland nut and replace with the grounding assembly, lightly threading the assembly onto the tube the assembly must match the tube size, i. Direct shielding is the only good method to deal with it.
Cable shielding and ground loops must be disassociated. Power, grounding, bonding, and audio for ham radio safety, hum, buzz, and rfi. This way, when the usb shield is zapped, the esd will bypass the psb and go to ground. Principles of electrical grounding john pfeiffer, p. At the pcb, the usb connector consists of 4 main signals. This is made possible with greater power generating capacity, however, this comes with an increased challenge of ensuring reliable data transmission. A floating shield provides no protection against interference. Tips on shielding and grounding in industrial automation. As described in 1 2 and 3, proper grounding techniques are necessary for safety, equipment operation and performance. Foil shielding used a thin layer of aluminum, typically attached to a carrier such as polyester to add strength and ruggedness.
I think those recommending resistors, or not connecting it to ground at all, or strictly talking about your digital logic ground, and assuming you have a separate shield ground. They help someone to regain their mental focus from an often intensely emotional state. A shield will reflect some energy, conduct some energy to ground, and pass some energy. Shielding techniques and cables the lab environment has many sources of electromagnetic interference, which must be avoided for sensitive electrical measurements. The angelus corporation has fulfilled the requirements for directorate of defense trade controls ddtc registration and compliance, and is fully compliant with u. Grounding and shielding for protection systems by david shafer skf usa inc. Effective grounding and shielding of amplifiers, voltmeters and enclosures will be covered. Cable shield grounding assembly installation instructions. Electrostatic discharge esd will be covered as it relates to equipment design. Usb com232plus1, it is best to avoid directly connecting the usb shield and signal ground on the pcb. In particular, usb has specific shielding, signal and power conductor requirements. Glenairs csga provide 360 emiemp grounding the first time. Improper grounds are responsible for more interference problems than any other condition. If an unshielded insulated cable is in contact with earth or a grounded.
As shown in figure 2, this presents shielding effectiveness. The multitude of app notes and articles on this subject that recommend grounding the shield at one end only misrepresent the physics of shielding and falsely ascribe a ground loop to the shield where the circuit itself was part of the original ground loop. Jun 07, 2017 proper grounding techniques of shielded ethernet cable. Over the years, ftdi have experienced that on designs where a standard usb ab or aminib cable is in use, such as with the.
The push for more electric aircraft is driven by weight savings and the availability of reliable electrical components. Shielding of power cables electrical engineering portal. Effectiveness of shield termination techniques tested with. Download it once and read it on your kindle device, pc, phones or tablets. Control the voltages developed on the ground when the. The metallic shield is the current carrying component that allows the insulation shield system to perform the functions mentioned earlier.
Grounding and shielding techniques wiley ieee, morrison. Grounding of shields can be a controversial subject because there are several ways to do it. Our line of cable shield grounding assemblies are available in male and female versions and provide completely reliable 360 grounding of shielded cables to above deck stuffing tubes and swage tubes. The myths that 1 a cable shield grounded at one end only single point. Some experimentation may be necessary to obtain the correct value. Device side cable shield connection i used to terminate the usb b connector housing to the system ground but now i am not sure. When referring to shield and grounding, in practice there are other ways of handling this subject, one with much controversy, as for example, the shield grounding can be made in each station with the sub d 9pin connector figure 34, where the connector housing makes contact with the shield and is grounded when connecting with the station. Incorrect wiring, grounding, or shielding can cause erratic servo performance or even a complete lack of operation.
Ft245r usb fifo ic datasheet usb fifo ic datasheet version 2. Each supports the other, overcoming the limitations of one with its own compensating strengths. Usb component emi design guidelines the following sections utilize the preceding strategies, applying emi reduction techniques as warranted, to the design of usb hosts, devices, hubs, and cables. When installing a protection system, numerous obstacles must be considered that are not an issue with smaller. For the shield to be effective, it requires as low impedance connection as possible to your shield ground. Use features like bookmarks, note taking and highlighting while reading grounding and shielding techniques wiley ieee. Symmetrical transmission techniques have numerous advantages in. Power supply noise reduction techniques need to be addressed also. Importance of grounding techniques 0 5 10 15 20 25 30 35 40 45 percent used grounding 42% case shield 22% cable shielding 18% filtering 12% pcb layout 6% grounding 42% case 22% cable 18% pcb 6% filter 12%. Question about usb port grounding and usb audio devices. The shield may be composed of braided strands of copper or other metal, such as aluminium, a nonbraided spiral winding of copper tape, or a layer of conducting polymer. Grounding and shielding techniques for emi, emc, and esd. Grounding grounding is a subject which is surprisingly complicated and is often poorly understand.
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