Wrist Strap is not just a Straps?

• What is wrist strap?

• How wrist strap work?

• How to use wrist strap?

• How to select wrist strap?

• How to test wrist strap?

• How to monitor the wrist strap?

What is wrist Strap?

The wrist strap is a device designed for keeping personnel at the same potential as sensitive items they are handling. Wrist strap consists of cuff, a stretchy band of fabric with fine conductive fibers woven into it or may be stainless steel with an attached cord. The fibers are usually made of carbon or carbon-filled rubber, and the strap is bound with a stainless steel clasp or plate. Wrist straps usually connect to Earth Bonding Points (part of the grounding system) via either a 4mm plug or 10mm press-stud.
wrist straps consits of

• Cuffs usually made of fabric with conductive fibers woven into it
  
• Metal plates usually hypoallergenic metal plate, stainless steel
• Resistor usually 1 Megaohm for current limiting
  
• Coil cord is a wire assembly
  
• Connection Plug, press-stud may be phono jack, banana jack, alligator clip

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 corrodes. And

How wrist strap work?
The wrist strap is a device used to prevent electrostatic discharge from our bodies to ESD susceptibility product by safely dissipates a person who working on electronics equipment.

The wrist strap is connected to ground through a coiled retractable cable and 1 mega ohm resistor added for safety purpose, 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 1 mega ohm is added in the path to ground to protect the wearer from excessive currents.

Type of Wrist strap

• Single Wire (cord) Wrist Strap is one wire (cord) that provides electrical connection of a person's skin to ground via 4 mm banana jack (plug) or alligator clip. It consists of a stretchy band of fabric with fine conductive fibers woven into it or (may be stainless steel) and the strap is bound with one stainless steel clasp or plate. If the wire (cord) is loose in their connection where ever, the wearer will not be connected to ground.
  
• Dual Wire Wrist Strap is two wires (cord) that provide electrical connection of a person's skin to ground via phono jack. It consists of a stretchy band of fabric with fine conductive fibers woven into it or (may be stainless steel) and the strap is bound with two separation stainless steel clasp or plate. If one of wire (cord) is loose in their connection where ever, the wearer will still be connected to ground with the other wire (cord).

Wrist strap realtime monitoring

While you are working with very ESD sensitive product, you may need an extra equipment so called Wrist Strap realtime monitoring. It will monitor connectivity of wrist strap and wearer to ground all the time. It will alarm with light and sound when loose of connection.