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We can null lead resistance in pF range caps.

Excellent video. This was briefly covered in my class, but we kept moving to other material.

Great graphics!

Thanks Mitch, well done - appreciated.

Thanks❤

can a bad neutral be upstream of the transformer?

I have been searching for a bad neutral for over a month,i bought a multimeter, I had the electric company come out, they said it is on my side, but the bad neutral is not steady it comes and goes, L1 has gone to 190 while L-2 was 50 , I did a ohms test yesterday on the neutral wire from meter pole to house.01 but from meter pole to transformer ohms read 2.5 in the morning and 3.5 in the evening, so my ? is that a normal reading

The old part of my Dad's house was (and still is) wired with an old 240 volt main and range pull out fuse panel with 4 screw in fuses, in 120 volt 15 - 20 amp circuits (small 5 room house when wired in 1949). Those 4 old circuits only have two conductor wiring - no ground wires. I know exactly what fuse turns off what light and what outlet- pretty straightforward and simple. Has a sub two circuit fuse box wired with 10-2 w/ground wire tapping off each 120 leg where the "handyman" used the ground wire as the neutral (installed in late 60's). I only figured this out on close inspection 20 years ago when my computer surge strip indicated no ground on these newer three prong "grounded" outlets in this addition. The "grounds" in these outlets had just been screwed back to the sub fuse box and ended there. So much for assuming the outlets were working three prong outlets. Anyways there is also one three prong outlet with newer type 12-2 with ground wiring on one of the old fused two wire circuits. Now this should have dawned on me sooner, knowing this circuit leaves the fuse box on old two conductor no ground wiring, that this particular outlet can't be grounded. I was working with this outlet and was running voltage checks before taking out the fuse, -hot to neutral, hot to ground, neutral ground. I could not believe it, but I was getting voltage readings on the neutral to ground???!!! (like 60 volts or whatever) and of course the hot to ground (but no where near 120). I was totally baffled as to what was going on. Of course pulling this circuits fuse out killed everything. I wasted several hours trying to get to the bottom of this. I even put one voltmeter probe on the nearby metal sink that is all plumbed with pvc in an all wood counter and could get volt readings. I was trying to figure out a way I could see if there something bad going on. It finally dawned on me that the ground wire couldn't (even though misleadingly attached to this outlet) be hooked up to anything and I was getting some wierd effect when checking voltage on neutral to ground with hot energized - with nothing plugged in or turned on in circuit. I simulated this out in my shop where I had one stand alone outlet hooked up to 20 feet of 12-2 w/ ground wiring in the breaker panel and disconnected this outlet's ground. I turned off all other circuits in box and was getting voltage readings in neutral to ground wires (way less than 120 of course). That was very interesting. This is also why I generally just kill everything whenever working on anything electrical. You just never totally know what has been done or what might be going on.

Get a fancier multimeter. Mine can be set to either 30Ω or 300Ω and also lets you set whether the tone is on or off for continuity or discontinuity. I can also set the voltage for diode testing to up to 3V or 15V.

Thanks

If you run on one leg L-1 and disconnect L-2 would you still have to have a neutral?

Gracias por usar guantes. ¡Me suscribo! 🧤 Thank you for wearing gloves. I subscribe! 👍

Wow insulated gloves in a demonstration. Seriously I can’t remember the last video where I saw insulated gloves. Well done!!

Thanks. I'm a JM spent most of my apprenticeship doing new commercial construction. That training was invaluable because u have to learn how buildings are built. Newayz. Man, when I moved to service the game changed! U gotta learn and learn quick. I learned this "ghost voltage" 2 yrs ago on a service call to a house. With breaker off I was still getting 30V on a fan/light switch. I intuitively knew it wasnt possible and even showed the homeowner I could lick my finger, ground myself out and touch the hot and nothing would happen. "dont do that handymen". I knew it was inductance but couldn't prove it at the time. Bothered me so I started doing research. In short learned about LowOZ meters and began teaching my apprentice about it. LowOZ is all I pack out now. Always working, always learning! Great video. Thank you.

You can get these phantom voltages in spades from cheapie SMPS modules. I have measured up to 1/2 line voltage on some. Sure, they only produce a few uA and while this is not enough to hurt anyone, it can destroy a MOSFET if it's applied to the gate. So, there are times when you need to take heed of these voltages and do something to mitigate them before you toast some sensitive equipment.

Good open neutral video. It should be pointed out that open neutrals have caused home fires in electronic equipment and in particular Metal Oxide Varistor transient protection devices. These can burn in an open neutral event during to current limited overvoltage. Breakers won't trip, as there's no overcurrent. This caused a rewriting of UL standards re these devices several decades ago. In switch mode power supplies which I designed years ago, we had several fires caused by mains through diode bridge connected Electrolytic caps. The 200 volt rated caps were grossly overvoltaged by the open neutral. The side vent snap-in lytics failed safe and released only vapors and smoke on overvoltage tests. Then purchasing got a good deal on an "equivalent " cap from a different mfg. These had a top vent, and nobody noticed myself included. Then we had a few fires caused by our products. Fortunately no deaths. In testing the failing caps we got the foil and flammable electrolyte to pop out of the top vent like a Flaming party favor. Didn't even blow the internal 3 Amp fuse! Today small power supplies and large are universal input, 90 to 260 vac, and use 400 volt rated Electrolytic caps, so open neutral fire incidents have come way down I'm happy to say.

Thank you! I need to buy a Loz meter it seems. I spent 8 hours chasing a phantom voltage the other day! It was 120v, I did IR, and it was fine, so touched it and had no shock, this is when I started looking at this ghost voltage phenomenon. Will I ever need to use the standard volts function again?

That was excellent..

I’m not an electrician, but I do some electrical work at home but I wanted to thank you for this video because it was very helpful. I’ll be keeping an eye out for your videos. Thanks.

My home developed a case of flickering lamps, some brighter, some dimmer. Also my cable TV and Internet service became quite intermittent. I measured my line voltages and when the loads were unbalanced one 120V leg dropped to 100V while the other 120V leg increased to 140V. In other words the neutral was at 20V rather than 0V. I used a 1200 Watt space heater to create an imbalance in load currents for testing. After getting the power company to send a lineman out to inspect and repair the connections at the utility pole, there is less than 1V on the neutral (relative to ground) when I test with the space heater. However, my Internet service was still very poor. The cable technician came out and discovered that about a two foot length of their coax drop cable was melted at the end up on the utility pole. My assumption is the unbalanced neutral current was flowing through the coax cable. Replacement of the coax restored proper Internet service. Fortunately I’ve had no other problems since.

How to calculate each phase voltage when loose neutral when unbalance load.

I had an issue some months ago with a new ceiling fan installation that had a remote control. The receivers kept burning out. When finally installing a standard fan without a remote a family member said that I had approximately 80v of ghost voltage and it was burning this solid-state receiver out. How do I get rid of ghost voltage?

Nicely explained Mitch, my understanding of electrical circuits has been broadened, this ghost voltage phenomena is clearly capacitive coupling at work, you saved a whole bunch of time, and guess work, thank you.

Learn something new everyday. I spent an hour+ chasing ghost voltage in some 14/3. Almost ended up cutting into drywall to run new wire; thought maybe I shorted a connector with a staple or something.

Is there an accepted range that voltage going to a device can vary? For example, can an 18v extension cord be used between 19v device and its 19v charger?

Why doesn't the neutral wire activate the tester? If I measure voltage with DMM between neutral and hot I get 120V. If I reverse the test leads, I still measure 120V. i.e. both hot and neutral carry alternating current.

3:56 - What does it mean on the Fluke when it gives a pulsating tone in the continuity setting?

yet another reason to baffle me why America persists in the two 110V split system.. there seem to be many hidden complications/ downsides and very few redeeming features

Good eve sir I have now encountered a problem with the LoZ when i test our outlet from the breaker it reads .1 ,and the crt of the lightings also .1 when we insert the circuit of the outlet inside the pipe of the ckt of the lightings,

Very interesting. The magnitism happens very quickly. Automatically. Shows how quickly current happens.

Thanks for the video

I didn't like one of the solutions proposed, de-energise adjacent circuits.. If there is an unintended short to one of them you will not then catch it. Regarding the voltage seen , lets say a good quality DVM has an input impedance of 10 M ohms, also lets guess at 100pF stray coupling capacitance. This would be ~25 Mohms at 60 Hz, so on a 110v circuit you would measure about 30v . If we had a 10 k ohm load we were measuring across we would see ~30mV (factor of 1000 Mohm to Kohm). If we looked across a live circuit we would dissipate 1.2 watts. You can buy DVMs with a low input impedance for precisely this job. this quick sum show its not an intractable problem

Another value that manufacturers do not usually show in their data is the voltage between the tips in diode mode, normally fluke has around 7V, klein uses 5V, but most generic multimeters use very little like 1.5 to 3V and that can be a problem measuring IGBT transistors as they do not have enough voltage to switch them.

It would be interesting to see the reading of an isolation transformer, normally in isolated ground circuits panel if we measure between L1 or L2 and the ground shows 60V when it should be 0V in theory because it is precisely isolated to avoid electric shocks in the patient of hospital.

The measured Ghost voltage measured 79VAC Phantom/ghost voltage from the white neutral wire of the power supply to the N/C white neutral wire of the cord and the same from the green earth wire of the power supply to the N/C green earth wire of the cord measured 79VAC phantom/ghost voltage. The question is why 79VAC is the phantom ghost voltage and not 120VAC? 120VAC real -79VAC ghost= 41VAC difference or loss.

Most Non-Contact testers only test AC voltages so you have to find DC voltage Non-Contact testers and also look into "insulation line break tester modes" to find a break/open in a wire harness or wire. Try making a YT lesson about using a DC non-contact tester and using the insulation line break mode to test wires, test relay contacts and test leaf type switch contacts because visually the contacts might look closed but won't have current passing through the switch contacts which the insulation line break tester will detect there is a BREAK

Continuity Mode doesn't measure the conductance value of various components or wire gauges plus most DVM meters give false readings when measuring below 2 ohms to milliohms. Example if you're measure Fan motor windings or compressor motor windings which are low ohms but various DVM meters will give false measurements because the range is not designed for low ohms. The DVM meter will measurement 2 ohms or 1.2 ohms for the compressor motor windings but is it really 2 ohms or 1.2 ohms? The DVM meters test voltage and test current might not be strong enough to get the correct measurement of certain motor windings that are designed that operate at a high voltage and high current.

Just to show that it *was* a Fluke, Mitch misnamed it twice. Thanks, LockPickingLawyer!

Great information

This is what I was explaining to a gentleman the other day. I was basically explaining to him that a noncontact voltage tester works off an electrostatic field. Whereas a clamp meter to sense current works off an electromagnetic field. You get an electrostatic field with the presence of voltage and you get an electromagnetic field with current flow. Michael Faraday demonstrated this phenomenon perfectly with a set of compasses placed in the proximity of a conductor that had current flowing through it in the early 19th century. This experiment also helped Michael Faraday discover the relationship between electricity and magnetism. Limited in his understanding of advanced mathematics, he commissioned James clerk Maxwell to write the famous maxwell equations explaining this phenomenon. The unit of electrical capacitance, “the Farad” is named after Michael Faraday. The unit of electrical inductance, “the Henry” is named after an electrical engineer by the name of Joseph Henry.

After a house fire my wife and I were staying in a camper trailer. It had a small freestanding refrigerator. My wife called me at work and told me the fridge was hopping up and down. I said to her I don’t know what you are talking about it cannot do that. I told her to unplug it. When I came home I plugged it in and it started to jump about. that thing weighed at least 60 pounds. After some investigation it turned out that the neutral wire in the incoming triplex had broken.Therefore no ground. I was told the voltage was hopping between 220 and zero.Hence there was enough energy to literally make it jump up and down. thankfully after a quick fix nothing had been harmed.

The Fluke Low Z impedance is 10K or 1K? The Low Z Meter loading is good for testing sense circuits, control circuits, AC or DC motors, open neutral unbalance loads circuits, power supply diodes and filter capacitors and coupling capacitor because the low Z meter loading is putting load. Coupling capacitors will block DC but the Low Z meter will put a load to test the "leakage" of the coupling capacitor which the High Z meter won't test the leakage of the capacitor give a false positive measurement. Same when testing an AC motor or DC motor the High Z meter will test the output Voltage of the motor but the Low Z meter is applying a meter loading so the motors output voltage will pull down sag so its testing the motor under load. Power supply rectifier diodes will test good with High Z meters but will fail with Low Z meters because the diodes is tested with the Meter loading which is testing the diodes Leakage. You should make YT video lesson about testing components with the Low Z meter testing under load.

Well done! Thank you. For fun I would have used 240 VAC and be careful.

Thanks a lot my entire house does this now I have a new project.

If the three phase source and neutral loost what hapens for the lightstreet

nice job.

Excellent demonstration

Thanks Man!

We had an open neutral which caused intermittent problems for a while. Eventually our main water line started leaking (buried in the yard). When the city came to replace the copper pipe they disconnected the ground strap, which they said drew an arc. That blew up some appliances, as the earth ground was acting as our neutral return, and once interrupted, caused unbalanced voltages just as in this demo. It's also nearly certain that the grounding currents eroded the water pipe over several months causing the leak. We had connection problems at the pole before, but this time the utility didn't even want to send a guy up to take a look. Even the electrician that the city sent out didn't seem to understand floating neutral hazards. Frustrating to me, as I'm an electrical engineer. All in all it was a $5k repair, which I had to eat.

I guess this would be a USA only problem, right? We don't have such problems in our fully 230v home circuits here in Europe.