ESD or Antistatic Wrist Strap is a protective device worn by personnel while working on sensitive electronic components in order to safely direct static electricity from their body to ground, and avoid equipment damage. This is because the antistatic wrist strap can avert the accumulation of static electricity, which can eventually lead to an electrostatic discharge.
Individually owned ESD wrist straps are typically to be connected to ground through a crocodile clip. On the other hand, those found in the industry normally connect to part of the grounding system or earth bonding points by either a 4 mm plug or 10 mm press stud.
Antistatic wrist straps are mainly used in the electronics industry by technicians working on electronic devices such as computers, which can be damaged by electrostatic discharge. In a less extensive manner, people working around explosives wear ESD wrist straps so that electric sparks that could trigger an explosion can be prevented.
Also, it should be used whenever trying to open equipment’s chassis, especially when handling circuit cards and electronic components. Moreover, the antistatic wrist strap must make good contact at equipment frame at one end and the person’s skin on the other for it to work as specified.
Furthermore, industries employ other ESD protective devices in conjunction with wrist straps. These devices include ESD floor mats and special vinyl floor tile and ankle straps. They are often used to allow personnel to move freely in a work area where a grounding cable would be bothersome.
Lastly, it is recommended to check the reliability of the device prior to using it, through an antistatic wrist strap tester, as there is a possibility that it could fail to perform its intended function.
Construction and Components
The antistatic wrist strap is basically composed of a flexible band of fabric with conductive fibers, which are generally made of carbon or carbon-filled rubber. Meanwhile, the strap is bound with a stainless steel clasp or plate.
In addition, a 1 MΩ resistor is added to the coiled retractable cable in order to permit high voltage charges to leak through but prevent an electrostatic shock hazard when working with low voltage components. Subsequently, extra resistance of 750 kΩ per 250 V is added in the ground path to protect the wearer from excessive currents when higher voltages are present.
Today, wireless ESD wrist straps that offer user mobility have proliferated in the market. They work on the principles of the so-called Selgard electric halo, corona discharge effect and skin effect. However, their reliability and effectiveness have been subject to criticisms from the conventional grounded design manufacturers and supporters.
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Antistatic Wrist Strap Instruction Manual: