标签: grounding

Once again, electrical engineers are at the forefront of a trend they were not even aware they were leading; and, once again, the outside world doesn't appreciate or acknowledge the EE's role.   According to a very skeptical article in The Wall Street Journal, " Products Aim to Connect People to Earth ," among the latest emerging fads is clothing and accessories that allegedly connect people to ground, a process sometimes called "earthing." (Note that we are talking about a true earth ground here -- not the circuit "common," which is often referred to as "ground" by engineers, even though there is no earth ground in the configuration, such as with battery-operated devices, cars, airplanes, to cite a few.)   It turns out that several companies are saying that because we live indoors and wear shoes, we have become "disconnected" from earth ground and thus are accumulating excess charge, which needs to be dissipated for our physical and mental well being. For example, Earth FX Inc. has bed sheets woven with conductive silver thread, which plug into the grounding contact on a three-terminal AC power receptacle (they also have some fascinating ground-only worldwide AC plugs, see here ), while Earth Listen Brands LLC offers footwear (flip flops and more, Figure) with soles having a circle infused with carbon powder, so they can (in theory) conduct charge between the user and earth ground.   The Pluggz flip flops from Earth Listen Brands LLC go a step further than regular footwear, with circles in the soles infused with carbon powder, allegedly to help conduct electrons between the earth and the wearer.   Now, almost every EE who does hands-on work with ICs at the test or prototype bench knows about the undeniable virtues of personal grounding to dissipate static charge buildup, and so prevent damage due to ESD such as blown ICs. The problem is not new, but it has gotten worse with the trend towards lower-voltage ICs and discrete devices, smaller-feature process geometries, and CMOS-based components. You only have to blow one or two such ICs due to ESD and waste time debugging or replacing parts to realize that you do need that grounding strap on your wrist and grounded work mat. You learn to keep that wrist strap available and to use it whenever you are handling those ICs.   Grounding is not just for sensitive components, either. Any time you have an AC-line connected device, you do have to make sure the line side and system chassis is grounded, unless it is specifically designed to function as an isolated device, as in the case of double-insulated tools, when making a floating voltage measurement of a single battery cell at the top of a stack of such cells, or biomedical equipment where the patient side must be 100% isolated from ground to prevent a fatal jolt if there is an internal short circuit.   The article quotes several medical doctors and electrical engineering professors about the purported personal-health virtues of this earthing phenomenon. These experts say that the body gains and loses electrons all the time, and the "earthing" is of no value at all.   But it doesn't note what EEs also know: Just because you have conductive soles on your shoes doesn't mean you actually have a good earth ground. In fact, establishing a good ground takes real effort, especially in areas where the soil is dry. A low-impedance path and quality earth ground may require an array rather than just a single pipe or rod. A poor ground connection won't help your circuit much, and certainly won't balance your personal charge.   This earthing is yet another example in a long line of pseudoscience techniques that play off of the public's fears, ignorance, and gullibility. The problem is separating legitimate issues from the scare ones. This is not an easy thing to do: For example, MRIs use intense magnetic fields, which temporarily affect the spin alignment of body's molecules (how an MRI creates an image is truly amazing); intuitively, this should be a bad thing for the body, yet there don't seem to be any harmful effects, regardless of the field intensity -- also amazing.   The good news is that while these earthing products won't do you any good, they won't do you any harm, either. They may, of course, actually create a feeling of well-being through the placebo effect and the power of suggestion.   What electronic devices have you seen that are based on highly speculative, if not outright faulty, premises such as personal earthing?

Electrical engineers are once again at the leading edge of a trend they didn't even know they were leading; and, once again, the outside world doesn't appreciate or acknowledge the EE's role.   According to a very skeptical article in The Wall Street Journal, " Products Aim to Connect People to Earth ," among the latest emerging fads is clothing and accessories that allegedly connect people to ground, a process sometimes called "earthing." (Note that we are talking about a true earth ground here -- not the circuit "common," which is often referred to as "ground" by engineers, even though there is no earth ground in the configuration, such as with battery-operated devices, cars, airplanes, to cite a few.)   It turns out that several companies are saying that because we live indoors and wear shoes, we have become "disconnected" from earth ground and thus are accumulating excess charge, which needs to be dissipated for our physical and mental well being. For example, Earth FX Inc. has bed sheets woven with conductive silver thread, which plug into the grounding contact on a three-terminal AC power receptacle (they also have some fascinating ground-only worldwide AC plugs, see here ), while Earth Listen Brands LLC offers footwear (flip flops and more, Figure) with soles having a circle infused with carbon powder, so they can (in theory) conduct charge between the user and earth ground.   The Pluggz flip flops from Earth Listen Brands LLC go a step further than regular footwear, with circles in the soles infused with carbon powder, allegedly to help conduct electrons between the earth and the wearer.   Now, almost every EE who does hands-on work with ICs at the test or prototype bench knows about the undeniable virtues of personal grounding to dissipate static charge buildup, and so prevent damage due to ESD such as blown ICs. The problem is not new, but it has gotten worse with the trend towards lower-voltage ICs and discrete devices, smaller-feature process geometries, and CMOS-based components. You only have to blow one or two such ICs due to ESD and waste time debugging or replacing parts to realize that you do need that grounding strap on your wrist and grounded work mat. You learn to keep that wrist strap available and to use it whenever you are handling those ICs.   Grounding is not just for sensitive components, either. Any time you have an AC-line connected device, you do have to make sure the line side and system chassis is grounded, unless it is specifically designed to function as an isolated device, as in the case of double-insulated tools, when making a floating voltage measurement of a single battery cell at the top of a stack of such cells, or biomedical equipment where the patient side must be 100% isolated from ground to prevent a fatal jolt if there is an internal short circuit.   The article quotes several medical doctors and electrical engineering professors about the purported personal-health virtues of this earthing phenomenon. These experts say that the body gains and loses electrons all the time, and the "earthing" is of no value at all.   But it doesn't note what EEs also know: Just because you have conductive soles on your shoes doesn't mean you actually have a good earth ground. In fact, establishing a good ground takes real effort, especially in areas where the soil is dry. A low-impedance path and quality earth ground may require an array rather than just a single pipe or rod. A poor ground connection won't help your circuit much, and certainly won't balance your personal charge.   This earthing is yet another example in a long line of pseudoscience techniques that play off of the public's fears, ignorance, and gullibility. The problem is separating legitimate issues from the scare ones. This is not an easy thing to do: For example, MRIs use intense magnetic fields, which temporarily affect the spin alignment of body's molecules (how an MRI creates an image is truly amazing); intuitively, this should be a bad thing for the body, yet there don't seem to be any harmful effects, regardless of the field intensity -- also amazing.   The good news is that while these earthing products won't do you any good, they won't do you any harm, either. They may, of course, actually create a feeling of well-being through the placebo effect and the power of suggestion.   What electronic devices have you seen that are based on highly speculative, if not outright faulty, premises such as personal earthing?