Welcome to Taking Measure (Electrical Testing and Troubleshooting). I'm Mitch Hegman, and I'm here to improve your knowledge, safety, and skills when using electrical testing tools.
Quality test instruments should be in the top drawer of an electrician or technician's toolbox. The adage "measure twice and cut once" doesn't apply solely to carpenters; instead, it's arguably more important for those who work with electrical circuits.
I'll cover everything from safety to techniques to test instrument features in my videos. Whether you're a beginner or a master electrician, there will be something of value to you in my tutorials and reviews.
Thank you for watching! Your feedback and suggestions are always welcome.
About
I'm a Master Electrician with an electrical career that spans 45 years- 28 in the field and 17 as a professional instructor.
My training clientele includes the IBEW, NECA, Boeing, NorthWestern Energy, the Federal Government, and the State of Montana.
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 very bottom line is this: If you are measuring wildly different voltages (not near 120V) from one line to neutral as opposed to the other line to neutral at a given point along the circuit or system, the open or poorly connected neutral is upstream to you. The ohm readings you shared seem a little wonky, but I really can't interpret from my distance. If you have stable voltages at the service at all times, the problem would be a poor connection on your side. If the voltage imbalance shows up on the utility service drop or lateral the problem is on the utility side. I have seen in many instances where a loose neutral connection at the service is the issue. This is especially true where aluminum conductors have not been installed properly. I hope this is of some help to you.
@@takingmeasure that's the downside of using an ohmmeter. I always "load" a suspect circuit or use the low range of a megohmeter, a high voltage ohmmeter used to ring circuits and motor windings. Regarding high resistance neutrals I use a 1500watt space heater on one of the phases and measure voltages everywhere and them move the space heater to the other phase and re-read voltages. That pinpoints the problems to the high resistance neutral.
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.
Many years ago, I had a somewhat similar experience the first time I encountered a ghost voltage. I wasted several hours "troubleshooting." Thank you for sharing your experience here.
I also realize without being able to physically track and see this wiring to never assume either. I don't remember if I decided to disconnect this ground because it probably wasn't doing anything and just to be safe, but I did note on outlet that it was NOT grounded. On another circuit I was fairly certain that the hot wiring went from fuse to light socket then to switch (light socket hot with switch off). I think a guy almost needs to have an independent grounded wire and rod while trying to sleuth down antique houses that have had decades of layering. I had another issue with a light not working in my Dad's boyhood farmhouse. This house had some lighting from a 32 volt DC light plant in the 30's and 40's. My recent understanding of these systems was that they generally used light sockets and outlets same as 120 stuff in anticipation of being wired up AC eventually. Might have been knob and tube. I have a couple of 32 volt farm radios that have the same cords/plugs basically as 120. This house had an old time 4 or 6 circuit breaker (!!!) panel. Still has two prong outlets etc. Twenty odd some years ago a new breaker panel was installed with wiring to energize old circuits in this panel with insides removed. Just tied to old house wiring that came into this box. I pulled down light fixture for this light and pulled out switch cover. This was even worse in that it was old rubber cloth stuff that as I recall didn't match what was in switch or old breaker box. Both wires looked alike basically. I couldn't make head or tales out of anything much less try to troubleshoot. I also hadn't really verified which outlets and lights were with what panel circuit etc. So I didn't have as clear of a picture. I also have no idea what work has been done over the years etc. I didn't waste a lot of time on that, never really got to bottom of this, and light started working again. I think I also put some ox guard on new breaker contacts in case this was the problem - aluminum bus bar in a dampish basement - original breakers were on first floor.
Makes me wonder why electricians don't use ox guard on new install everything as it is all pretty much aluminum now and so prone to oxidation / resistance heating / poor contact arcing issues. I seen this in a 20 year old breaker box in a building at my dad's with a 100 amp main breaker chewing up the contact on the bus bar about 20 years ago. I was told 30 years ago by an electrician to use ox guard on the aluminum stuff I was installing at that time. He also told me to run the underground aluminum cable in a drain tile to protect it. My dad also had a 20 year old buried aluminum cable fail 20 years ago too. It was all under a lawn. Another guy year ago told me how some mobile homes from 70's (??) had aluminum wiring and the terminal ends of this wiring would get hot and burn them down - oxidation.
@@wdmm94 Using a voltage tester or meter with a low impedance input will tell you for certain. The ghost voltage is partially the function of the high impedance input of the DMM or tester.
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.
Thank you for watching and posting the comment. Given my type of work, I would not often require the features you suggest, but I am impressed with the idea. Thanks again!
From the point downstream from where the neutral is open, the circuit is completed by way of L-2. If L-2 is not present, you would simply have an open circuit.
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.
Thank you for the comment. Early in my career, I spent a good part of a day chasing a ghost voltage. They can be tricky and someone needs to teach you about them.. I am pleased that you are teaching others about this and anything else that is of helpful. Good stuff!
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.
Thank you for the comment. Because I was dealing with power distribution equipment, ghost voltages were more a nuisance than anything, but at your level of circuity I can see how problematic this can be. Again, thank you for sharing this.
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 for the comment. I have seen a lot of strange and dangerous events caused by open neutrals over the years. I really appreciate your take on this. I find myself ever-thankful for UL standards an the constant quest to revise them as required.
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?
Thank you for watching. For troubleshooting basic branch circuits, common lighting circuits, etc., a low-Z meter is great (helpful). But if you are working with circuits that may be impacted due to "meter loading," you would want to use a high impedance instrument. As example, I recently talked with the operator of a powerplant, who told me about technician who knocked the generator off-line by attempting to measure voltage on a relay control circuit with a low-Z meter. In this case, a high impedance instrument should have been used.
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.
Thanks for sharing your story. An interesting one at that! I am glad you were able to get the connections back in order before more serious imbalances caused great damage.
To calculate the voltage dropped across any point, you need to know the total series resistance of the circuit path as a starting point. Using that, you can calculate total current. Using ohms law, you can apply that to the resistance of each side (E = I x R) to determine the voltage drop.
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?
A ghost voltage is really an "illusion" of voltage produced by the meter. The voltage is not actually present in the circuit being tested. To eliminate a ghost voltage you can simply take measure with a low impedance meter. I suspect something other than a ghost voltage is responsible for damage to your remote. Hopefully you can find the cause soon.
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?
The short answer is "yes," every device has a range of voltage in which it can safely and effectively operate. Various codes and manufacturing standards may apply to any given device. I believe, for example, The National Electrical Manufacturers Association standards recommend that motors should be designed to operate satisfactorily at a voltage variation of plus or minus 10 percent. Other devices or equipment may be more tolerant or less tolerant of voltage variation. This is really a case-by-case matter.
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.
The neutral is a grounded conductor. Grounded wires are designed to have a low resistance path to the ground, which means they are essentially at the same potential as the ground itself. Therefore, there is no potential difference (voltage) between the grounded wire and the surrounding environment. As a result, a non-contact voltage tester will not detect any voltage on grounded wires because there is no electric field emanating from them. Put in simple terms: the electrostatic charge is not allowed to build.
If it does so while simply holding the probes together, the DMM may need servicing. If it does so while connected to a circuit, it could indicate intermittent continuity. You may want to see if the display is also giving a fluctuating ohm reading (if you are within the range of indication).
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,
I am not certain I am following you entirely. But the first thing I would do is test voltage on a known energized circuit to confirm the meter is working properly. Also make certain you are wearing proper personal protective equipment when doing so.
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
Your point is valid. There may also be a lot of instances where it would be impractical or undesirable to de-energize adjacent conductors. Life-safety circuits, for example. Thank you for the comment.
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.
Thank you for sharing this comment. Even in DMMs constructed to accepted and adopted standards, the differences in underlying manufacturing parameters for each instrument can be problematic.
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.
That's a physical phenomenon! I told you the 79V depends on many factors. The 2 wires are not touching. A good electrical engineer could probably calculate that voltage using Maxwell equations.@@waynegram8907
The value of the ghost voltage is related to the length of the wire capacitively coupled with the energized ungrounded wire. We might see a voltage nearer to 120V if the "floating" wire was longer and provided more capacitance when coupled. A mush shorter wire would yield less voltage. It might be fun to do a lab on this...
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.
Thank you for watching and commenting. I didn't understand the limitations of continuity test until someone showed me. I am suspect a lot of DMM users are unaware of this.
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.
Well said. The study of electricity is interesting stuff. Under each layer of what you see (and know) there is always another to further explain things. I am still learning after all these years. Thank you for watching and thank you for the comment.
@@takingmeasure thank you for posting this video and your comment, sir! Yesterday I registered for my first class at the local community college to start my 4 year journey in obtaining my electrical engineering degree from Mississippi State University’s Bagley college of engineering.
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.
I am not certain about the exact value of input impedance for the Fluke 117, but it is a feature I really like. I use Low Z mode for basic voltage measurements: testing receptacle circuit voltage, etc. I like your suggestion for going deeper into the various issues and results when using either high impedance measurement mode or the Low Z setting on specific components or circuits. There is no end to this stuff. Thanks for the comment!.
@@takingmeasure If you look at different products the label on the back will say how much current consumption it takes to energize or power on the circuit. Different types of loads can measure the same DC resistance value but will draw different amounts of current which is the main differences between different types of loads. Different types of loads will measure DC resistance lets say 100K resistance but each different type of load will draw and consume a different amount of current. Examples a Vacuum, toaster, Scanner Fax machine, Vegetable Steamer, lets say all measure DC resistance as 100K load but each load is going to consume and draw a different amount of current. An Analog meter simpson 260 has meter loading effects and so does the fluke 117, but how much current is it consuming and drawing. Something to think about to make a YT lesson about because its not about the Loads DC resistance but also the Loads current draw consumption.
@@takingmeasure When using the Fluke meter in Low Z mode connect a Current clamp around the RED probe to measure the current consumption of the current under test. If the current under test is 1K and the Fluke meter low Z mode is 1K which is 1K/IK= Half the supply voltage or source voltage. If the current under test is 10K and the Fluke meter low Z mode is 1K that is 10K/10+IK = V out . The Voltage divider RATIO keeps changing depending on the circuit under test TOTAL resistance which changes the RATIO of the voltage divider. You can use the current clamp to connect around the Fluke DVM meter RED or Black Probe to measure the current draw and the measured voltage which V/I = Meters Low Z Resistance. Something to think about to make a YT lesson about.
Poor electrical connections, improper grounding and bonding, and distribution equipment failure can lead to strange voltage imbalances. Some of this can damage wiring and any connected appliances and devices. When someone tells me they are experiencing strange voltage fluctuations, I always recommend shutting down anything they can. I also recommend getting help troubleshooting from a professional for those who are not in the trades.
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.
Yours is the type of story am sorry to hear. Electricity will find a way to return to the source as best it can. The fact you would up with a $5k bill adds insult to injury, I expect. I appreciate that you shared the story with us. Thank you.
Thanks for the very informative video. This is scary. I've been working with low power electronic equipment for many years. I don't get involved with house wiring. I didn't realize the hazard in the neutral connection.
As with any wiring system, 120/240V systems are reliable and safe when installed and functioning as designed (per Code). But if "unusual" voltage events seem to be occurring on such systems, I always recommend shutting down what loads you can, not operating any switches, and calling a professional to troubleshoot as soon as possible. Thank you for watching and commenting.
sir you did not mention the stated capacitance of the small capacitors, ergo could not match with the measuring instrument values. Furthermore you did not measure the small capacitors with the yellow multimeter. please make a detailed video. 👍👷🙏
Simpson analog meters would use the RX1 or RX10 or RX100 to measure capacitors and what the analog needle to see any fluctuations when the capacitor is getting charged. Many capacitors will pass test on capacitor meters but will fail the Simpson Analog meters fluctuation test. Using low impedance capacitor testers that puts a LOAD on the capacitor will fail leaky capacitors. On the oscilloscope you measure the capacitor but using a Function generators Square waveform and measure the ramp time divided by voltage = capacitances
Simpson analog meters were the first test instruments I used. They are very well built and accurate if properly cared for. I did not have much call to test capacitors with them. Thank you for sharing your knowledge!
@@takingmeasure Yes its in the Simpson Analog Meters testing manuals or other service manuals that would use simpson analog meters to test capacitors and diodes resistance test. Diodes can test good using a DVM meter 0.7vdc but the test current test voltage is very low. Simpson RX1, RX10, RX100 scale has different test current test voltage for diodes resistance. The diode will pass the forward voltage test but will FAIL the diode resistance test.
The KLEIN and FLUKE meter should be very high impedance, so it shouldn't discharge the capacitor unless the capacitor has a high ESR. A good capacitor will keep the charge stable and not discharge. This is how you test very large capacitance that are out of the DVM meters capacitance range. If a capacitor is 10,000uf you can't test it using a DVM meter in capacitance mode so you have to apply the operating rated voltage using a power supply then removing it and let the capacitor still for an hour and come back to measure the DC voltage and it should be very stable not discharging at all.
