Power, grounding, bonding, and audio for ham radio safety, hum, buzz, and rfi. 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. The angelus corporation has fulfilled the requirements for directorate of defense trade controls ddtc registration and compliance, and is fully compliant with u. Control the voltages developed on the ground when the. This appendix describes some of the most important sources of interference and summarizes cabling and shielding techniques used to reduce pickup. You should always have a connection to earth ground, for personnel safety. Usb device cable shield connection grounding it or not. A floating shield provides no protection against interference. Jun 07, 2017 proper grounding techniques of shielded ethernet cable. Symmetrical transmission techniques have numerous advantages in. 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. The correct place to connect an electrostatic shield is at the reference potential of the circuitry contained within the shield.
If you have a metal enclosure, this will be your shield ground. This is the layer where various cable types differ most. Glenairs csga provide 360 emiemp grounding the first time. Some experimentation may be necessary to obtain the correct value. For that reason, most cables are named after their metallic shield e. The net result of these instructions, is to isolate the pcb ground plane from the usb shield. As shown in figure 2, this presents shielding effectiveness.
Since 1994, he has helped thousands unravel the mysteries of grounding and signal. Question about usb port grounding and usb audio devices i have a rocksmith usb real tone cable, which is basically just a usb soundcard hardwired to be usb dongleguitar jack. Grounding and shielding of amplifier, bridgesensor and voltsensor input leads noise can couple into lowlevel signals in a variety of ways. 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. I tried different certified usb cable but their connection of cable shield to connector shield was done totally bad and useless for emc immunity and reliability. The metallic shield is the current carrying component that allows the insulation shield system to perform the functions mentioned earlier. Grounding and shielding this article was written for calex by mr. Grounding and shielding techniques wiley ieee kindle edition by morrison, ralph.
Grounding of shields can be a controversial subject because there are several ways to do it. Ralph morrison, president of instrum and the author of grounding and shielding techniques in instrumentation published by wiley. 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. Bonding the usb cable shield to gnd on both ends is the best only way to deal with that. Grounding and shielding techniques for emi, emc, and esd. Improper grounds are responsible for more interference problems than any other condition. 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. This note summarizes the proper techniques and is intended as a. A shield will reflect some energy, conduct some energy to ground, and pass some energy. Grounding is a set of simple strategies to detach from emotional pain for example, drug cravings, selfharm impulses, anger, sadness. Wiring, grounding, and shieldingtechniques proper wiring, grounding, and shielding techniques are important in obtaining proper servo operation and performance. Use filtering on those lines, such as power and ground, that cannot be kept clean. 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. 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.
Techniques for measuring shielding effectiveness will be addressed. Practical grounding, bonding, shielding and surge protection practical professional books g vijayaraghavan, mark brown, malcolm barnes on. 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%. Tips on shielding and grounding in industrial automation. Usb hardware design guidelines for ftdi ics ftdi chip. 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. I think those recommending resistors, or not connecting. Grounding demystified 3 2 categories of solutions applied for compliance. This way, when the usb shield is zapped, the esd will bypass the psb and go to ground.
Grounding and shielding techniques wiley ieee, morrison. 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. Each supports the other, overcoming the limitations of one with its own compensating strengths. Effectiveness of shield termination techniques tested with tem cell and bulk current injection arthur t. Medium and highvoltage power cables, in circuits over 2000 volts, usually have a shield layer of copper or aluminum tape or conducting polymer.
A shielded cable is an electrical cable of one or more insulated conductors enclosed by a common conductive layer. This is made possible with greater power generating capacity, however, this comes with an increased challenge of ensuring reliable data transmission. Usb com232plus1, it is best to avoid directly connecting the usb shield and signal ground on the pcb. Incorrect wiring, grounding, or shielding can cause erratic servo performance or even a complete lack of operation. The practice showed, that the biggest problem is to find quality usb cable. Device side cable shield connection i used to terminate the usb b connector housing to the system ground but now i am not sure. The angelus corporation is committed to complying with all united states export laws and regulations. The push for more electric aircraft is driven by weight savings and the availability of reliable electrical components.
It also provide personal safety and protect the equipment. Effective grounding and shielding of amplifiers, voltmeters and enclosures will be covered. If an unshielded insulated cable is in contact with earth or a grounded. Cable shield grounding assembly installation instructions. They help someone to regain their mental focus from an often intensely emotional state. Shielding techniques and cables the lab environment has many sources of electromagnetic interference, which must be avoided for sensitive electrical measurements. Principles of electrical grounding john pfeiffer, p. Ft245r usb fifo ic datasheet usb fifo ic datasheet version 2. This helps isolate it and reduces emi and rfi emissions.
Cable shielding and ground loops must be disassociated. Grounding and shielding for protection systems by david shafer skf usa inc. Power supply noise reduction techniques need to be addressed also. Grounding is a technique that helps keep someone in the present. Cable shield grounding assembly installation instructions attention. Download it once and read it on your kindle device, pc, phones or tablets. In particular, usb has specific shielding, signal and power conductor requirements. You can also think of it as distraction, centering, a safe place, looking. Effectiveness of shield termination techniques tested with. Power, grounding, bonding, and audio for ham radio safety. The usb universal serial bus specification defines the mechanical and. More power flowing through the aircraft means higher levels of electromagnetic interference emi.
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. There are two types of shielding typically used for cables. Question about usb port grounding and usb audio devices. 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. 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.
The user selected grounding scheme for usb devices, and cables must be consistent with accepted industry practices and regulatory agency standards for safety and emiesdrfi. Over the years, ftdi have experienced that on designs where a standard usb ab or aminib cable is in use, such as with the. Foil shielding used a thin layer of aluminum, typically attached to a carrier such as polyester to add strength and ruggedness. Practical grounding, bonding, shielding and surge protection. 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. They help reorient a person to the hereandnow and in reality. Understanding shielded cable page 3 a third approach, seen in alpha wires suprashield products, combines both foil and braid shields in protecting the cable. Use features like bookmarks, note taking and highlighting while reading grounding and shielding techniques wiley ieee. For the shield to be effective, it requires as low impedance connection as possible to your shield ground. Grounding grounding is a subject which is surprisingly complicated and is often poorly understand. Cable shield grounded at one end only emc standards. 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. Distraction works by focusing outward on the external worldrather than inward toward the self. 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.
The myths that 1 a cable shield grounded at one end only single point. When installing a protection system, numerous obstacles must be considered that are not an issue with smaller. To limit the usb cable antenna effect, it is recommended to connect the shield and ground through an rc filter. Shielding of power cables electrical engineering portal. Direct shielding is the only good method to deal with it. Connect the shield at the source switch end of the cable only. Bureau of industrial security bis export administration regulations ear and requirements. Grounding skills can be helpful in managing overhelming feelings or intense anxiety.
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