Antistatic wrist strap
Encyclopedia
An antistatic wrist strap, ESD wrist strap, or ground bracelet is an antistatic device
used to safely ground
a person working on very sensitive electronic
equipment, to prevent the buildup of static electricity
on their body, which can result in electrostatic discharge
(ESD). It is used in the electronics industry by workers working on electronic devices which can be damaged by ESD, and also sometimes by people working around explosives, to prevent electric spark
s which could set off an explosion. It consists of a stretchy band of fabric
with fine conductive fibers woven into it. The fibers are usually made of carbon or carbon-filled rubber, and the strap is bound with a stainless steel clasp or plate. They are usually used in conjunction with an antistatic mat
on the workbench, or a special static-dissipating plastic laminate on the workbench surface.
The wrist strap is usually worn on the nondominant hand (the left wrist for a right-handed person). It is connected to ground through a coiled retractable cable and 1 megohm resistor
, which allows high-voltage charges to leak through but prevents a shock hazard when working with low-voltage parts. Where higher voltages are present, extra resistance (0.75 megohm per 250 V) is added in the path to ground to protect the wearer from excessive currents; this typically takes the form of a 4 megohm resistor in the coiled cable (or, more usually, a 2 megohm resistor at each end). Very cheap wrist straps do not have conductive fabric and instead use the fabric to hold the metal plate against the skin, which can result in reduced ESD protection over time as the metal corrode
s.
Wrist straps in industry usually connect to Earth Bonding Points (part of the grounding system) via either a 4 mm plug or 10 mm press stud, whereas personally owned straps are likely to be connected to ground via a crocodile clip
.
In addition to wrist straps, ankle and heel straps are used in industry to bleed away accumulated charge from a body. These devices are usually not tethered to earth ground, but instead incorporate high resistance in their construction, and work by dissipating electrical charge to special floor tiles. Such straps are used when workers need to be mobile in a work area and a grounding cable would get in the way, such as in an operating theatre
.
Wireless or Dissipative wrist straps are available, but they are widely considered as pseudoscientific hoax products. The claims of the operating principles vary from "Ion Neutralization, Skin Effect, Point Discharge and Corona Discharge Effect" to "Selglard electric halo principles".
Antistatic device
An antistatic device is any item which has the effect of reducing static electricity charges on a person's body or equipment, either to prevent fires and explosions when working with flammable liquids and gases, or to prevent damage to static-sensitive objects such as electronic components or devices...
used to safely ground
Ground (electricity)
In electrical engineering, ground or earth may be the reference point in an electrical circuit from which other voltages are measured, or a common return path for electric current, or a direct physical connection to the Earth....
a person working on very sensitive electronic
Electronics
Electronics is the branch of science, engineering and technology that deals with electrical circuits involving active electrical components such as vacuum tubes, transistors, diodes and integrated circuits, and associated passive interconnection technologies...
equipment, to prevent the buildup of static electricity
Static electricity
Static electricity refers to the build-up of electric charge on the surface of objects. The static charges remain on an object until they either bleed off to ground or are quickly neutralized by a discharge. Static electricity can be contrasted with current electricity, which can be delivered...
on their body, which can result in electrostatic discharge
Electrostatic discharge
Electrostatic discharge is a serious issue in solid state electronics, such as integrated circuits. Integrated circuits are made from semiconductor materials such as silicon and insulating materials such as silicon dioxide...
(ESD). It is used in the electronics industry by workers working on electronic devices which can be damaged by ESD, and also sometimes by people working around explosives, to prevent electric spark
Electric spark
An electric spark is a type of electrostatic discharge that occurs when an electric field creates an ionized electrically conductive channel in air producing a brief emission of light and sound. A spark is formed when the electric field strength exceeds the dielectric field strength of air...
s which could set off an explosion. It consists of a stretchy band of fabric
Textile
A textile or cloth is a flexible woven material consisting of a network of natural or artificial fibres often referred to as thread or yarn. Yarn is produced by spinning raw fibres of wool, flax, cotton, or other material to produce long strands...
with fine conductive fibers woven into it. The fibers are usually made of carbon or carbon-filled rubber, and the strap is bound with a stainless steel clasp or plate. They are usually used in conjunction with an antistatic mat
Antistatic mat
An antistatic floor mat or ground mat is one of a number of antistatic devices designed to help eliminate static electricity. It does this by having a conductive material embedded within the mat that collects the static. The mat would need to be grounded . This is usually accomplished by plugging...
on the workbench, or a special static-dissipating plastic laminate on the workbench surface.
Resistor
A linear resistor is a linear, passive two-terminal electrical component that implements electrical resistance as a circuit element.The current through a resistor is in direct proportion to the voltage across the resistor's terminals. Thus, the ratio of the voltage applied across a resistor's...
, which allows high-voltage charges to leak through but prevents a shock hazard when working with low-voltage parts. Where higher voltages are present, extra resistance (0.75 megohm per 250 V) is added in the path to ground to protect the wearer from excessive currents; this typically takes the form of a 4 megohm resistor in the coiled cable (or, more usually, a 2 megohm resistor at each end). Very cheap wrist straps do not have conductive fabric and instead use the fabric to hold the metal plate against the skin, which can result in reduced ESD protection over time as the metal corrode
Corrosion
Corrosion is the disintegration of an engineered material into its constituent atoms due to chemical reactions with its surroundings. In the most common use of the word, this means electrochemical oxidation of metals in reaction with an oxidant such as oxygen...
s.
Wrist straps in industry usually connect to Earth Bonding Points (part of the grounding system) via either a 4 mm plug or 10 mm press stud, whereas personally owned straps are likely to be connected to ground via a crocodile clip
Crocodile clip
thumb|Standard clipthumb|Pair of standard clipsA crocodile clip is a simple mechanical device for creating a temporary electrical connector, and is named for its resemblance to an alligator's or crocodile's jaws...
.
In addition to wrist straps, ankle and heel straps are used in industry to bleed away accumulated charge from a body. These devices are usually not tethered to earth ground, but instead incorporate high resistance in their construction, and work by dissipating electrical charge to special floor tiles. Such straps are used when workers need to be mobile in a work area and a grounding cable would get in the way, such as in an operating theatre
Operating theatre
An operating theater was a non-sterile, tiered theater or amphitheater in which students and other spectators could watch surgeons perform surgery...
.
Wireless or Dissipative wrist straps are available, but they are widely considered as pseudoscientific hoax products. The claims of the operating principles vary from "Ion Neutralization, Skin Effect, Point Discharge and Corona Discharge Effect" to "Selglard electric halo principles".
See also
- Antistatic deviceAntistatic deviceAn antistatic device is any item which has the effect of reducing static electricity charges on a person's body or equipment, either to prevent fires and explosions when working with flammable liquids and gases, or to prevent damage to static-sensitive objects such as electronic components or devices...
- Antistatic bagAntistatic bagAn antistatic bag is a bag used for shipping components, which are prone to damage caused by electrostatic discharge.These bags are usually plastic and have a distinctive color . The polyethylene variant may also take the form of foam or bubble wrap, either as sheets or bags...
- Antistatic garmentsAntistatic garmentsAnti-static garments or anti-static clothing is required to prevent damage to electrical components or to prevent fires and explosions when working with flammable liquids and gases.- Electrostatic sensitive device :...
- Antistatic agentAntistatic agentAn antistatic agent is a compound used for treatment of materials or their surfaces in order to reduce or eliminate buildup of static electricity generally caused by the triboelectric effect. Its role is to make the surface or the material itself slightly conductive, either by being conductive...
- Antistatic matAntistatic matAn antistatic floor mat or ground mat is one of a number of antistatic devices designed to help eliminate static electricity. It does this by having a conductive material embedded within the mat that collects the static. The mat would need to be grounded . This is usually accomplished by plugging...
- Antistatic bag
- Electrostatic sensitive deviceElectrostatic sensitive deviceAn electrostatic-sensitive device is any component which can be damaged by common static charges which build up on people, tools, and other non-conductors or semiconductors...