At one time I had a very nice (expensive) multimeter... a co-worker asked if he could borrow it to do some continuity checks on his truck... I asked him numerous times if he would disconnect or remove the battery so that he didn't accidentally kill the meter. He brought it back to me and told me it didn't work. He was correct, in that it no longer worked. He had tried to measure resistance of a live loaded circuit. It was the last time I loaned a meter to anyone.
Have you...say...contacted Fluke ? Simple really. https://www.fluke.com/en-us/support/calibration-services Mike
Man Steve, you got that right! Section 250 of the code is enough to make an engineer look for another line of work! I've always tried to simplify the grounding and bonding thing. We ground the service and bond almost everything else. Of course then go and read 250 and shake your head.
I also suspect the meter is being influenced by the generator voltage or waveform. I have one that selects AC/DC automatically also. When working on my trailer lights a few weeks ago it was showing only 6 volts (approximately) on the turn signals, but 12.x on the brakes, tail and stop. finally figured out that it was seeing the 'blink' as a square wave AC and averaging the value. It is possible that your generator is not a sine wave output and is causing the meter to do something similar.
When I was in the water well service business (what a horrible way to make a living) we had a "suspect" voltage meter. Being in a pretty rural are we are serviced by an electric co-operative. We took the meter to the electric company office and their people were at least able to tell us if it was reading correctly, and if it was off, just how "off" it was. We were of the opinion that they would have some pretty reliable meters. Not calibration like you originally asked about, but at least a pretty simple check. Lynn
There was definitely some very pissed-off women. I heard a Colonel's wife soiled herself (and the shower stall) when she got hit, that put the search into overdrive.... Had a similar deal with a neighbor. I get a panicked Sunday-morning call from the husband, his wife got knocked over when washing dishes. Seems they had breakfast, she started cleaning up and he went out to do some maintenance at their pump house. All of a sudden there's 90 volts at the sink (way more than enough to get your undivided attention) that literally knocked her on her ass. I assumed he had gotten into the electrical somehow but he hadn't. Turns out a buddy who claimed knowledge installed a light in the pumphouse and when he couldn't find a neutral (there wasn't one, as the pump was 220V), he used the ground as a neutral. Hubby goes to the pumphouse, turns on the light, and Mama just happens to be elbow-deep in soapy water... ZAP! Turn off the light, the voltage disappears...
I never thought of that! I am the common denominator in these two multimeters! Naw... that couldn’t be it, but I do have trouble using a “ stud finder”! Lol Bones
Made this test a while back, a cheap DMM and an oscilloscope hooked up to the AC alternator output on a small twostroke bike. These are regulated to 12V by being shorted to ground long enough to bring the average voltage down to the correct level when the unregulated generator output is higher due to a low load and/or high rpm. The reason I made the video was relating to the very high peak voltages these can put out even when everything is correct (they kill LED lights that way), but it also shows that non TRMS DMMs can get very confused when they are fed anything but a proper 50-60Hz sine wave. The first ten seconds (lights on, limited regulation) the DMM gives a somewhat resonable reading up to 13V, when I kill the lights after 10 seconds the regulator really messes up the wave form and the DMM goes down to 8V despite the actual TRMS voltage still is about 13V. The irony is that an old analog meter does not have this issue.
Years ago we were installing some VERY expensive Medical Imaging Equipment at a VA Hospital. The equipment is 480V 3phase. When installing this type of equipment there are certain requirements the SITE MUST provide. Floors so flat, floor loading, electrical. As we go to "hook up" the power we can see the site's electrician has provided us a Ground by tapping into the neutral buss in the room's panel. Old building no ground in panel. This was a deal breaker for us as our equipment specifications are quite clear. The electrician argued with us that Neutral and Ground were and I quote "No different". We went 'round and 'round and finally said we're gonna need to talk to your boss. So they send in the "Electrical Engineer of Record" for the BUILDING who immediately made the SAME argument. Keep in mind -I'm mechanical - and even I knew better. We had to threaten to pull their multimillion dollar equipment out before they would run the second wire. It was hysterical. This is your I'm sorry OUR tax dollars at work. As an outsider it was a hard place to work - one guy would be completely incompetent and the next guy would be awesome. You NEVER knew who'd you get.
Here's the thing that someone needs to explain. Every electrical circuit must have a ground to complete the circuit or electricity doesn't flow. If you don't install a local ground .........current residing in the hot wire will flow thru the "neutral" wire and the circuit will work. If the "neutral" wire is not returning to ground, then how can current flow? Not trying to be a smart a** but I don't see the difference. In cars there isn't any "neutral" wire.......just a hot wire going thru a fuse panel......then thru a component.....and on to ground.
Cars are 12 Volts Direct current - If you make a body connection from +12 Volts to ground, it will not kill you (I can put one hand on the "+" battery terminal and the other hand on the "-" terminal and not feel anything. Alternating house and industrial voltages are 110 Volts and up. It can kill you if your body contacts a "hot" wire and another body part is touching a ground. The "neutral" wire returns the power from the "hot" wire and everything works safely. If the "hot" wire accidentally contacts the case of the equipment the case becomes hot - this was what happened in the previous example of the shocking kitchen sink. The "ground" wire is a safety wire that is connected to the case of the equipment. If the "hot" wire accidentally touches the equipment case, the circuit breaker trips (much cheaper than the OSHA fine for electrocuting a worker). Note: A GFI (Ground Fault Interrupter) requires a "ground" wire to work properly - I highly recommend pushing the "TEST' button to verify that it works before pluging any equipment into a GFI outlet. Russ
In a single voltage AC circuit or any DC circuit, no 'ground' or 'neutral' is electrically required. All you need is a circuit path out to the device from the power supply and one back to the power supply. It's when you have dual voltages that a neutral and ground is required. And as has been already discussed, 'ground' wires on branch circuits are required as a safety feature. But that's not all they do. A typical household service is 110/220V. There's three incoming wires from the utility; two 'hots' and a neutral. If everything is working right, you'll have 110V to the ground/neutral from each hot, and 220V between the two hots. This where a properly bonded ground becomes critical. To get dual voltage, the transformer coil is tapped exactly in its center and that's where the neutral is attached. So from one end of the coil to the other is 220V, either end to the midpoint is 110V, again if everything is correct. This midpoint is connected to the earth ground at the main panel, and that anchors the midpoint in place, insuring that it will always be 110V to either hot. So what happens if this anchor is lost? You now have what is known as a 'floating neutral' and that's bad news... Top diagram is a properly-anchored neutral, you have 'normal' voltage to the lamps. Let's assume that each lamp is the same size/wattage. Now obviously the two-lamp circuit will draw twice the current of the single lamp circuit. The lower diagram is the same circuits/lamps, but the 'anchor' is missing, there's no path to ground and the neutral is 'floating'. You still have the same 220V between the two hots, but because the individual lamp loads are equal, they divide the voltage equally between them. So the two on the left will get very bright (and probably burn out), the right side one will go dim. If you added a fourth lamp of the same size on the right side, the load would be 'balanced' and you wouldn't see any difference. If you want to kill a bunch of electronics fast, float the neutral... I killed three box vans worth of computers/monitors/printers in about 30 seconds one time that way.... long story. You can get the same effect by opening up a shared neutral at a junction box with hot circuits. This clear it up?
Actually they don't require a ground wire. How those work is they measure the current going out and compare it to the current coming back and if it varies by more than their threshold (usually about 25 milliamps) they trip. If you have an old home with two-wire outlets and want to add three-wire grounding outlets without rewiring, GFI outlets are approved for that use.
Did not know that, a new trick for this old dog. I would have to look up the wiring diagram - Don't own anything that old - going to file that in the "Unsolved mysteries" file... Recently worked on a 46 year old house that my daughter bought. The "TEST" button did not work, had to chase back 2 outlets to find the missing ground (was never connected). Russ
How long ago was this? There's a pair of "electricians" that aren't worth their title. There's a section in the NEC specifically for medical facilities, and neither of them apparently have/had any idea it existed.. If I'm not mistaken, medical facilities are required to have dedicated grounds run to most, if not all, of their circuits. That aside, the wiring they supplied was wrong anyway, right along with their claim that neutral and ground was no different from each other. Now, a circuit will work when using the ground as a current carrying, return path conductor, but it's still wrong. Roger
We always need a complete circuit for current to flow. Nothing more, nothing less. Neutral is just the place we say we have zero volts, just like we say sea level is zero altitude. A more or less imaginary point of reference. Safety ground in the high voltage wiring in a house is an alternate path to neutral used only for safety purposes, it is connected to things that may get connected to "hot voltage" in case of a fault (such as the metal outside of the kitchen stove) so such a fault becomes a short and blows the fuse rather than kill anyone who touches it. Cars don't have such a ground. They have neutral (zero volts, most often battery negative but sometimes positive in a few old systems) connected to the chassis.
Thank you to each of the above people who have taken the time to help me understand these electrical situations. I understand better now......I think.
I can tell you from personal experience of doing jobs at a couple of VA facilities that the competence of their plant maintenance staff is iffy at best. But I also found that they're not always the ones in control. Hospitals are run by doctors and run into one with a God complex who wants what he wants when he wants it and having the HP to get his way, you'll run into stuff like this. I knew a electrician who took a 'maintenance' job at a large local hospital when construction was slow. He was handed a install of a piece of new equipment ordered by a department head (a Dr). There was two major issues; one, the wall the Dr wanted it hung on wasn't structurally capable of supporting it. And two, same issue with the power supply as noted above. He presented these issues in order to correct them, when the Dr found out this would delay the install and go over budget, he ordered the guy to go ahead anyway. The electrician refused, the Dr got him fired, the cowed guys that were left did it his way... The fired guy told me he was told the equipment ripped out of the wall after about six months....
Kinda overstated. They don't need to cover every possible electrical situation when they are trying to dumb it down so even a simpleton like me can understand.
Yes this is made confusing inpart because of the differences in AC (Alternating Current) and DC (Direct Current). In DC (as used by our automobiles) yes we work with circuits that must contain a "Hot" and a "Ground". In AC circuits - a Ground and Neutral are basically a redundant set of wires. And while they are redundant they are also DIFFERENT. One designed to carry current in normal use and the other designed as a safety (Hence the term safety ground) that is used to minimize your hazards. Once you start adding additional phases it gets even more confusing. For example - a 120V circuit consists (at a minimum) of a Hot and a Neutral. A 240V circuit typically consists of 2 120V legs - 180degrees out of phase that when added result in 240V - this circuit works on those two "hot" no neutral needed. Neutral is just a reference point. Measure your 240v circuit from one hot to neutral and you get a reading of 120v. Hot to Hot and you get 240V. Throw 3 phase in there and it gets even more confusing. This is where diagrams serve greatly in explaining the differences. But to simplify - the ground NORMALLY doesn't carry current. That's why a 240V single phase can consist of 3 wires - two hots and a safety ground. That ground is NOT normally carrying current, the circuti completes between the two hots. I recently ran into an issue with my welder. It was wired 240V - 3 wire - (no neutral) and I wanted to add a 120V water cooler. But HOW? I know better than running it between a Hot and Ground (that would work but is a no-no) - so instead I added a step down transformer going from 240v to 120v. Now had the supply been 4 wire - 2 hots a neutral and a ground I wouldn't have had to mess around with a trnsformer. Make sense? Hey if not - my excuse it - I'm MECHANICAL!!!!!
It wasn't all that long ago - I bet they both still work there - after all its the VA - it'd probably take an act of congress to fire anyone there. Our system requirements were CLEAR - these guys? I'd bet neither could spell NEC much less know what it was and IF they by some miracle did know what it was - neither had ever read it. I mean running into a dumbass electrician is as likely as running into a dumbass in any profession, but when the Electrical Engineer of Record for the entire building was just as stupid - yes it was one of THOSE moments.
Back when I bought a place in the “big city” that was built in the early ‘60’s everything was two wire. Seems along the years 3 prong plugs were installed I never could find the real ground. After some time when I had had issues under the house, I saw what the “person” did. They tied the ground for everything to the water pipes. Mercy. So think about what would happen if joe the plumber was doing his thing, and a short occurred. Joe wouldn’t be happy Now at that time I didn’t know what I knew some years later. But knew that wasn’t right. Having grown up in the country and pulling ground rods out with my dad as a kid, I called PGE to see what I needed to do So they told me “no issue”. They came out and dig up around my water meter, installed a different one so they could use a plastic? Isolater where my water main went into the meter Hmnn. I went back under, took apart what I saw and buried a ground rod. Panel was wired correctly best I could see. But always have to be careful about what works and what’s safe. Kinda like cinder blocks are not good car stands
That used to be a typical grounding method and was probably legal at the time. Up until I retired, there was multiple choices in the NEC in what you could use as a earth ground and that is probably still true. Metal water piping could be used as long as X amount was in contact with earth, driven ground rods, bonded rebar located in a poured foundation base, ground grids, and even gas piping in certain instances although this one was discouraged. But driven ground rods were/are popular because of ease of installation and checking said install, plus it was unlikely that any subsequent work would disturb them. But it was also possible that individual localities could change those requirements. The NEC is only an 'advisory' document with no force in law unless adopted by the local 'authority having jurisdiction' and they're free to make any changes they see fit and many do for local conditions. I'll also point out that utilities don't fall under the NEC as a general rule. They're free to do whatever they want. A quick example is most transformers that utilities mount on poles for overhead services are horribly undersized for the load as per the NEC. Locally, they use a 15KW transformer that if I installed it would be limited to a 70 amp load. They'll power two 200 amp services off it....
For the other electrically challenged individuals (like me) out there, I find this to be very handy and inexpensive. Just touch the two wires on something and it tells you something.........
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