Cutting Through the Static
There are many definitions of static, none of them desirable in the context of installation and service activities – especially pertaining to electricity. Learn techniques to minimize potential damage and even danger from this source.
“Star Wars” made “The Force” something you always wanted with you. However, there is another type of force that technicians ought never to covet. It’s a force that has been around since the beginning of time and can wreak havoc with many of today’s low power electronic components, circuits and devices. Electrostatic charges create dangerous force fields that can result in what is known as an electrostatic discharge or ESD.
With the winter months approaching, the incidence of equipment damage from ESD will substantially increase due to reduced humidity in the air. We all become familiar with ESD as children after walking across a rug and touching things like a metal stud on a fireplace or a lamp frame and then got zapped by a blast of miniature lighting. While entertaining, this same type of ESD can result in damage to electronics or millions of dollars in property, and even death if careful attention is not paid.
Thus, this month we will look at how security dealers can save equipment, property and lives, and even make some extra revenue, from managing the effects of ESD.
Common Causes of ESD
One of the causes of ESD is static electricity. It is the act of tribocharging; the separation of electrical charges when material is brought together and then separated. A work-related example of this would be the pulling of tape from itself on a spool or walking across a rug or vinyl floor.
Another cause of ESD damage is through electrostatic induction. This happens when electrically charged items are placed near a conductive object that is isolated from ground. An example of this would come from items such as Styrofoam cups or plastic bags.
While the most popular form of ESD is the proverbial spark, many ESD-sensitive electronic components can be critically or fatally damaged with an electrical discharge of as little as 10V potential. This invisible event would not be felt or heard by a human.
Steps to Reduce Servicing Risks
Today’s alarm tech has many new technology tasks, including servicing a variety of computer equipment. Preventing ESD when servicing electronic equipment can be applied at several levels. It all depends on how thorough the technician wants to be in minimizing the risk of ESD damage.
Remember that the goal when handling and servicing electronic components is not to introduce a voltage potential, either from your body or neighboring insulative objects, to sensitive electronics and systems.
One simple technique to prevent ESD that most of us may have used through the years is making sure you touch the metal PC chassis before touching any sensitive areas, such as handling plug-in PC circuit boards. Is this correct? If your answer is yes, you are not completely right; there is more to this process that we often realize.
It is normal practice when changing out PC boards to remove the AC power by pulling the power cord. This helps avoid any accidental incidents with live power. However, by doing this you have also removed the electrical earth ground and the PC chassis is now floating; not a good source for discharging the electrostatic buildup in your body. It’s very important to find a good earth ground to touch before handling sensitive equipment.
A possible discharge source could be touching the AC outlet cover plate screw (assuming the earth ground is good on the AC outlet). You must also remember to discharge again any time you move, handle plastics or get up to walk around.
One very important ESD prevention tool in every experienced PC serviceman’s bag is an ESD wrist strap used for safely grounding yourself (see photo). Just remember that you must have a good earth ground to properly discharge before handling sensitive electronics. One handy little inexpensive device for this is the Qube ESD ground adapter plug from Prostat Corp. (prostatcorp.com). It allows you to easily plug your ESD wrist strap into the ground pin of an AC outlet.
Do you know if the AC outlet ground is good? How? Did you test it with your AC outlet tester? Don’t have one? Shame on you, you should have one for testing all your AC connections. A good source for a tester is Ideal’s E-Z outlet checker (idealindustries.com).
If you do a lot of field service assembly work on ESD-sensitive components, you may also want to look at an ESD pad that will allow you to create an ESD-safe work area. The pad plugs into the same neutrally charged bonded circuit. You may also want to consider a more professional configuration such as the Desco AC analyzer and wrist strap tester combo unit. It is competitively priced (see Tool Tip).
You can further minimize ESD risk by practicing some additional service tips. Make sure to keep circuit boards in closed ESD-protective bags until you are discharged and ready to insert or replace. Handle boards by the edge. Be careful with static-producing actions like removing tape from a spool, and inductive items like normal plastic bags and Styrofoam cups.
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