You know what it’s like! You grab the door handle unsuspectingly, and bzzz – electricity strikes. What happens here is called electrostatic discharge (ESD). Of course, the question arises as to how this ESD came about. Why do people charge themselves in the first place? Just how dangerous is electrostatic discharge, and what protective measures are there? We’ll explain everything you need to know about this phenomenon.
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So what is electrostatic discharge?
Ever had your hair stood on end after putting on a sweater? Do you get “wiped” by your fellow human beings or your car from time to time? This phenomenon is called electrostatic discharge.
It is often abbreviated with ESD for the English term electrostatic discharge. In colloquial terms, we mainly talk about an “electric shock”. And that’s precisely what an electrostatic discharge is: a high, short electric shock.
If and how strongly we notice the electrostatic discharge depends on the voltage:
- Above 3000 V: the discharge is perceptible to humans (e.g. door handle).
- Above 5000 V: the discharge is audible (e.g. when taking off crackling sweaters)
- Above 10000 V: the discharge is visible in the form of a spark or lightning (e.g. thunderstorm)
Therefore, electrostatic discharge is a balancing of the electrical charge towards an electrical conductor or towards the earth.
Note: ESD can quickly cause voltages of over 10000 V to occur in modern work areas. These are not dangerous for people but destroy electronic components.
What causes people to become electrically charged?
As said before, many phenomena exist where we feel that we are or have been electrically charged. If, for instance, we walk across a carpeted floor and then touch the door handle, an electric shock is inevitable.
Why is this? What causes people to become electrically charged? Each body has a large number of electrical charges. We do not notice any of this, though, because the effects of the positive and negative charges cancel each other out. To the outside, our body is neutral or uncharged.
To charge a body, the charge must either be transferred to it or taken away from it. This is possible, for instance, by friction.
Already the ancient Greeks knew this. They discovered that if you rub a piece of amber against wool, it attracts small objects. The old Greek word for amber is “Elektron”. Correct, the relationship to the word “electricity” is no coincidence!
Examples of electric charge in everyday life
Let’s go back to everyday life: For example, when you rub a balloon against a woolen cloth, then the balloon picks up negatively charged electrons from the woolen cloth. So, wool cloth loses electrons, and the balloon has an excess of electrons. Over time, it is negatively charged.
That negative charge aims to balance itself out and uses contact with the first electrical conductor – a metal door handle – to drain away and restore equilibrium.
Similarly, if you walk across a carpeted floor, the friction between your shoes and the carpet causes them to pick up negatively charged electrons. In time, you become negatively charged, and if you then reach for the doorknob, your charge jumps from you to the doorknob. You get an electric shock.
Note: rubber soles insulate from the floor and thus promote electrostatic charging on carpeted floors. Leather soles tend not to have this problem because they dissipate the electricity.
What is the best way to determine whether a body is charged electrically?
To determine whether a body is electrically charged before a noticeable discharge occurs, you need an electrical measuring instrument: an electroscope. If an electrically charged body is held up to an electroscope, the pointer of the electroscope will move accordingly.
The electroscope allows you to detect an electric charge, but it can also measure it. The electroscope scale provided for this purpose is called an electrometer.
What is the best way to discharge an electrically positively charged body?
If your colleagues’ hair is out of reach or you are not in a joking mood and want to get rid of the electrostatic charge quickly, look for a metal cabinet or a heater.
Put your entire palm on the white part of the radiator or metal surface. The bigger the metal or radiator surface, the less you will feel from the discharge.
The whole thing works for prevention, too, of course: If you do not want to be really charged in the first place, then discharge regularly to be on the safe side.
Tip: Do your clothes often destroy your hairstyle in the morning? Against electrically charged clothes, a metallic clothes hanger will help. Before putting it on, stroke the metal hanger through your garment from the inside to discharge the fabric via the metal.
Could static discharge be dangerous?
In our everyday lives, most of our encounters with static discharge tend to be funny or hair-raising, sometimes even going unnoticed by us. However, ESD poses a serious risk in factories and laboratories.
In fact, even these discharges, which are not noticeable to humans, damage sensitive electrical components. Electronic component structures are so small that the consequences of even small discharges can be compared to the effect of lightning on a tree.
Larger discharges can cause sparks to form. If flammable substances are involved, sparking can cause an explosion or fire in the worst case.
By the way, even the mere shock situation caused by an electric shock can be dangerous in some areas. Drop your coffee cup in the kitchen in fright, and the cleaning job that follows is your biggest annoyance. Just a few seconds of carelessness or rash movements can lead to accidents in operation.
Note: typical ESD damage, such as premature component failure, is usually undetected by the manufacturer at the factory. Frequently, the damage is only noticed at the customer’s premises. So not only do the actual repair costs then have to be paid, returns and other replacements quickly become expensive fun.
What is ESD protection?
So electrostatic discharge is dangerous and can also be costly. But which measures contribute to ESD protection?
There are two main approaches to ESD protection:
- Avoid charges
- Avoid rapid discharges
There is no subsequent risk of electrostatic discharge, no matter where charges can be avoided. For example, an electrostatic charge can be avoided by dissipating or grounding bodies.
If a body is once electrostatically charged, it is the nature of things that sooner or later, a discharge will occur. However, although the discharge cannot be avoided, it is possible to influence the speed and thus the intensity of the discharge. For example, with large electrical resistances, it is possible for existing charges to flow away slowly.
Which ESD protection measures are available?
The amateur electrician might only take one or two effective measures. Hence, businesses often have to devise entire ESD protection concepts. Many different measures are available for implementing ESD protection.
Typically, ESD protection measures are:
- Person-related protective measures (e.g., ESD clothing, ESD shoes, ESD wristbands, ESD tools).
- Work-related protective measures (e.g. antistatic and dissipative work surfaces, ESD flooring, ESD seating).
- ESD protection programs (e.g., employee training, establishing and reviewing protective measures).
Whereas personal and work-related protective measures are concrete applications, ESD protection programs deal with administrative tasks to provide for the necessary ESD equipment and employee training.
The exact measures to be implemented depending on the specific environment and the building components used. While establishing a complete ESD protection zone may seem excessive for an amateur electrician, ESD poses a great risk in many industry sectors, and individual ESD measures such as ESD clothing alone are not enough.
So how does an ESD strap work?
An ESD or antistatic strap can set up a person’s grounding quickly and easily. For instance, the strap is connected to the bare metal of a heating thermostat. If you do not want to work tethered to the heater or it is simply too far away, a ground rail provides a more elegant solution like those found on lab benches.
It’s easy to understand how an ESD strap works: If your body becomes electrostatically charged during work, the charge can flow off directly via the wrist strap connected to a grounding bar. Charges, therefore, do not accumulate in the first place and are always discharged directly.
Furthermore, the ESD band has a high electrical resistance of 1 MΩ, which impedes the current’s path to the ground. The charge is guaranteed to flow away slowly, and no large currents can occur.
Note: Unlike WLAN, wireless connection does not work with ESD tape. So please don’t trust the tempting idea of wireless ESD wristbands; simply, they lack the cable through which the charge can flow away.
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The bottom line: Small charges, great damage
Electrostatic discharge is a phenomenon that everyone encounters sooner or later in everyday life. Occasionally, the short, high electrical shock that results can be felt, felt, heard, and even seen. With crackling sweaters and conductive doorknobs, you can usually get away with a new haircut or a minor scare.
However, ESD can wreak havoc in other fields, such as industry. Numerous ESD protection measures are available to protect sensitive building components and prevent unnoticed damage. The goal here is to prevent both charges and rapid discharges.
There are measures against electrostatic discharge directly for people and also in workplace design. Typical means such as ESD clothing, specific shoes and floor coverings allow charges to creep peacefully into the ground without noticeably harming their wearers.
