07-04-2003, 04:39 PM
Hi,
In my original post, I said, "making sure that you are wearing a grounding strap connected to the case." and, "Connect one end of a grounding strap to that lug, the other end to the computer".
Now, I was using the term "grounding strap" in two different senses here. In the first case, I meant the standard anti-static wrist strap and wire with clip that can be purchased at any electronics store. This typically has an in-line resistance of a few hundred kilohm to a few megohms. This "strap" is what is used to ground the *person* to the case and the in-line resistance is a necessary safety feature. If one is going to distinguish between a "grounding strap" and a "static discharge clip", then it is in this case that I should have been corrected but wasn't. My feeble defense is that we always just called these devices "grounding straps".
The second sense in which I used the phrase "grounding strap", I meant just a wire with clips at each end. One clip on the vacuum nozzle, the other to the computer chassis. No additional resistance. This was the use that I was challenged on and I defended it in my reply. If I was at all at fault, it was for failing to stress that power should be off *and unplugged* when using this device (or, indeed, whenever working inside the computer except for troubleshooting). However, as I replied before, this is not a dangerous condition. Indeed, it is exactly the condition that occurs whenever using any electrical device that is grounded by a third wire. If something does occur, the electricity follows the path through the ground (which is very low resistance) instead of through the person (which is a much higher resistance). Furthermore, in dry air conditions, the airflow through an insulating nozzle can generate a *lot* of static charge, enough that the potential across a megger can build up to a few tens of volts -- more than enough to kill many MOS circuits. So, my advice stands as written and for what I consider valid reasons.
--Pete
In my original post, I said, "making sure that you are wearing a grounding strap connected to the case." and, "Connect one end of a grounding strap to that lug, the other end to the computer".
Now, I was using the term "grounding strap" in two different senses here. In the first case, I meant the standard anti-static wrist strap and wire with clip that can be purchased at any electronics store. This typically has an in-line resistance of a few hundred kilohm to a few megohms. This "strap" is what is used to ground the *person* to the case and the in-line resistance is a necessary safety feature. If one is going to distinguish between a "grounding strap" and a "static discharge clip", then it is in this case that I should have been corrected but wasn't. My feeble defense is that we always just called these devices "grounding straps".
The second sense in which I used the phrase "grounding strap", I meant just a wire with clips at each end. One clip on the vacuum nozzle, the other to the computer chassis. No additional resistance. This was the use that I was challenged on and I defended it in my reply. If I was at all at fault, it was for failing to stress that power should be off *and unplugged* when using this device (or, indeed, whenever working inside the computer except for troubleshooting). However, as I replied before, this is not a dangerous condition. Indeed, it is exactly the condition that occurs whenever using any electrical device that is grounded by a third wire. If something does occur, the electricity follows the path through the ground (which is very low resistance) instead of through the person (which is a much higher resistance). Furthermore, in dry air conditions, the airflow through an insulating nozzle can generate a *lot* of static charge, enough that the potential across a megger can build up to a few tens of volts -- more than enough to kill many MOS circuits. So, my advice stands as written and for what I consider valid reasons.
--Pete
How big was the aquarium in Noah's ark?