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With a ground megger
Ground spike under a tire.... (Unsafe grounding practices)
- Thread starter chrisf
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They should. They're also used for testing insulation. They might not want to lend it to you, they're lovely devices for shocking the unwary (It's like an ohmeter, only much higher voltage, most test at 600V and 1000V), but ask them to demonstrate it to you.
Compare the earth connection with the spike under the tire on ashphalt to a spike pounded into dirt.
Compare the earth connection with the spike under the tire on ashphalt to a spike pounded into dirt.
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MOOXE said:
It is as good a ground as the guy leaning against the truck smoking is. I don't know about you but I would prefer if my troops were not the path of least resistance. An earth megger is standard kit in a Line shop.
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Hi everyone,
I know this is a stupid question, but I'm going to be teaching a class on electrical safety, and I'd much rather look like an idiot here than in front of my class. :blotto: Basically, I'm wondering whether it's safe to touch the ground spike. I have always been told that it's not, and one of the safety principles on this old lesson plan I'm going off of is "Never touch the ground spike!" But, it was my understanding that a ground spike simply provides a pathway to transfer excess electrical charge from the equipment into the ground, and that consequently, touching the ground spike would be no worse than touching the equipment itself. Am I just missing something here?
Thanks for any answers you can provide!
I know this is a stupid question, but I'm going to be teaching a class on electrical safety, and I'd much rather look like an idiot here than in front of my class. :blotto: Basically, I'm wondering whether it's safe to touch the ground spike. I have always been told that it's not, and one of the safety principles on this old lesson plan I'm going off of is "Never touch the ground spike!" But, it was my understanding that a ground spike simply provides a pathway to transfer excess electrical charge from the equipment into the ground, and that consequently, touching the ground spike would be no worse than touching the equipment itself. Am I just missing something here?
Thanks for any answers you can provide!
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To me this is like asking the question whether or not it is safe to hold onto the antenna when someone transmits. It is not safe. Electricity will find the path of less resistance. That could land up being you.
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The ground spike connects the vehicle to the ground (earth, point of zero potential).
Provided the spike firmly pounded, and ground wire is properly connected, there is little to no danger in touching it, is a much lower resistance path to earth than you are.
It's when there's a fault in the system somwhere you've got a problem.
If there's a break in the path of the grounding connection, happens frequently at the nut which attaches the spike to the wire, then there is potential for shock, as you may become the ground. That being said, if there is a break in the break in the grounding connection, exactly the same danger is present from touching ANY part of the now ungrounded vehicle as from touching the grounding wire (Ever been shcocked from a vehicle with a bad ground you try to climb onto it? It's unpleasent, and this is why, you're providing a path to earth)
It's slightly different from touching a transmitting antenna, as the antenna itself ungrounded, it has no path to ground. Say for example you're standing on a metal vehicle shelter roof, or on the deck of an AFV. Either one of those things will a different potential than the transmitting antenna, on touching the antenna, current will travel through you to the point of lower potential.
End result, the result of danger from touching a ground spike is about same as the danger in touching a vehicle itself.
Provided the spike firmly pounded, and ground wire is properly connected, there is little to no danger in touching it, is a much lower resistance path to earth than you are.
It's when there's a fault in the system somwhere you've got a problem.
If there's a break in the path of the grounding connection, happens frequently at the nut which attaches the spike to the wire, then there is potential for shock, as you may become the ground. That being said, if there is a break in the break in the grounding connection, exactly the same danger is present from touching ANY part of the now ungrounded vehicle as from touching the grounding wire (Ever been shcocked from a vehicle with a bad ground you try to climb onto it? It's unpleasent, and this is why, you're providing a path to earth)
It's slightly different from touching a transmitting antenna, as the antenna itself ungrounded, it has no path to ground. Say for example you're standing on a metal vehicle shelter roof, or on the deck of an AFV. Either one of those things will a different potential than the transmitting antenna, on touching the antenna, current will travel through you to the point of lower potential.
End result, the result of danger from touching a ground spike is about same as the danger in touching a vehicle itself.
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Regarding touching a transmitting antenna; while it's possible you might get a shock from a transmitting antenna, it's likely to be a high voltage/low current shock, which will wake you up but not injure you. The concern about touching a transmitting antenna is the RF burn you'll likely receive, which will hurt like a regular burn. At higher transmitting powers, you don't even need to be touching the antenna to receive a burn...much like being microwaved. Not pleasant!
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I was going to paste a link to the wikipedia article on electric shock, but it's really badly written. Really really badly written. Even by wikipedia standards.
I would love to know who produced the flaming hot dog pic though.
Oh, and bleating goat, check your private messages (Should be a link at the top of the page).
I would love to know who produced the flaming hot dog pic though.
Oh, and bleating goat, check your private messages (Should be a link at the top of the page).
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Anything that awesome was definitly before my time.
We both know that PETA had nothing to do with the ban, at some point, somone definitly looked at it, unzipped their pants, etc, and then no more hot dog cookers.
I had a few scanned from some OLD (Turn of the last century) electrical code books a while back... I've heard stories of "old timer" electricians using their fingers to check for voltage, and being able to tell you how much was there by how it felt... one of these books explains how to check for voltage with your fingers, and suggests an alternative method of building a voltage tester if you weren't manly enough take the pain... another suggested that a quick finger up the rectum was the best method for reviving somone from electrical shock...
We both know that PETA had nothing to do with the ban, at some point, somone definitly looked at it, unzipped their pants, etc, and then no more hot dog cookers.
I had a few scanned from some OLD (Turn of the last century) electrical code books a while back... I've heard stories of "old timer" electricians using their fingers to check for voltage, and being able to tell you how much was there by how it felt... one of these books explains how to check for voltage with your fingers, and suggests an alternative method of building a voltage tester if you weren't manly enough take the pain... another suggested that a quick finger up the rectum was the best method for reviving somone from electrical shock...
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I once watched a man with a screw driver taped to the end of a wooden broom stick short circuit a capacitor about as big as a family sized soup can... I'm not sure if it was appropriate to laugh, but the look of sheer terror in his eyes just made it funny at the time.
I couldn't find the original scan, but I found a quote from the pages... (Disclaimer: Don't do this at home kids. Call an electrician. If you absolutely have to mess about with electricity, and refuse to get a professional, master-craft meters are usually on sale for $20 at Canadian tire.)
"The American Electricians Handbook (1942) A Reference Book for Practical Electrical Workers. Terrell Croft, consulting engineer. McGraw Hill Book Company, Inc, New York and London 1942
Electricians often test circuits for the presence of voltage touching the conductors with the fingers. This method is safe where the voltage does not exceed 250 and is often very convenient for locating a blown-out fuse or for ascertaining whether or not a circuit is alive. Some men can endure the electric shock that results without discomfort whereas others cannot. Therefore, the method is not feasible in some cases. Which are the outside wires and which is the neutral wire of a 115/230 volt three wire system can be determined in this way by noting the intensity of the shock that results by touching different pairs of wires with the fingers. Use the method with caution and be certain that the voltage of the circuit does not exceed 250 before touching the conductors.
159. The presence of low voltages can be determined by testing. The method is feasible only where the pressure is but a few volts and hence is used only in bell and signal work. Where the voltage is very low, the bared ends of the conductors constituting the 2 sides of the circuit are held a short distance apart on the tongue. If voltage is present a peculiar mildly burning sensation result, which will never be forgotten after one has experienced it. The taste is due to the electrolytic decomposition of the liquids on the tongue which produces a salt having a taste. With voltages of 4 or 5 volts, due to as many cells of a battery, it is best to test for the presence of voltage by holding one of the bared conductors in the hand an touching the other to the tongue. Where a terminal of the battery is grounded, often a taste can be detected by standing on moist ground and touching a conductor from the other battery terminal to the tongue. Care should be exercised to prevent the 2 conductor ends from touching each other at the tongue, for it they do a spark can result that may burn."
I couldn't find the original scan, but I found a quote from the pages... (Disclaimer: Don't do this at home kids. Call an electrician. If you absolutely have to mess about with electricity, and refuse to get a professional, master-craft meters are usually on sale for $20 at Canadian tire.)
"The American Electricians Handbook (1942) A Reference Book for Practical Electrical Workers. Terrell Croft, consulting engineer. McGraw Hill Book Company, Inc, New York and London 1942
Electricians often test circuits for the presence of voltage touching the conductors with the fingers. This method is safe where the voltage does not exceed 250 and is often very convenient for locating a blown-out fuse or for ascertaining whether or not a circuit is alive. Some men can endure the electric shock that results without discomfort whereas others cannot. Therefore, the method is not feasible in some cases. Which are the outside wires and which is the neutral wire of a 115/230 volt three wire system can be determined in this way by noting the intensity of the shock that results by touching different pairs of wires with the fingers. Use the method with caution and be certain that the voltage of the circuit does not exceed 250 before touching the conductors.
159. The presence of low voltages can be determined by testing. The method is feasible only where the pressure is but a few volts and hence is used only in bell and signal work. Where the voltage is very low, the bared ends of the conductors constituting the 2 sides of the circuit are held a short distance apart on the tongue. If voltage is present a peculiar mildly burning sensation result, which will never be forgotten after one has experienced it. The taste is due to the electrolytic decomposition of the liquids on the tongue which produces a salt having a taste. With voltages of 4 or 5 volts, due to as many cells of a battery, it is best to test for the presence of voltage by holding one of the bared conductors in the hand an touching the other to the tongue. Where a terminal of the battery is grounded, often a taste can be detected by standing on moist ground and touching a conductor from the other battery terminal to the tongue. Care should be exercised to prevent the 2 conductor ends from touching each other at the tongue, for it they do a spark can result that may burn."
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a Sig Op said:
This is not quite true. The ground spike is still dangerous when dealing with large currents (such as from a short circuit, wire or lightning strike).
The issue comes from the fact that impedence and resistance in a conductor can increase when the conductor comes under high currents. A good analogy for electricity and conductors is that of wires and pipes. A ground spike, with a 8 gage wire, is a rather large pipe for electricity. However if the current is large enough, the "pipe" might not be enough to allow all that current to flow smoothly. If you grab the ground spike, you become an alternate source of grounding, which electricity might use, should the main ground be less than ideal to deal with the current. You, in effect, be come part of a grounding array.
In short, while the ground spike, in good working order and properly installed, might be sufficent for general radio use if you are touching it, should a unusual amount of current be sent to ground, you may be putting yourself up as ONE of the paths of least resistance.
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It also means that if you are touching any part of the truck and the ground you are at the same risk. The insulating properties of the tires only work if you are fully in/on the truck, otherwise you are acting as a secondary grounding point. This is why we use a ground spike, otherwise the veh would retain the voltage.
