Category ratings are based on the meters ability to withstand transient voltage spikes and not have the meter fail internally and become a short or point of arc fault on system. The closer you are to the utility the more robust your meter input protection needs to be to prevent dielectric failure causing a dangerous fault condition in the meter. The more equipment a transient such as a lightning strike has to go through the more it is attenuated. The industry has broken buildings into category’s. Category 1 being the farthest from the utility with the least residual transient voltage and Category 4 being at the utility interface with little drop in transient voltage. The impedance you are talking about is not in the meter it is the impedance from the source to your location. IE. your service connection will have less impedance including all the connections and length of wire, by the time you get to an outlet in an upstairs bedroom you may have much more. So a transient spike traveling through these environments will have less energy as it travels through the building. The input protection is designed accordingly. There is nothing wrong with using a category 1 meter on your service wire connections unless a voltage spike hits the system and creates a fault in the meter that is connected to your mains power, which could create a real short circuit condition with lots of current available. The issue is you don’t know when that transient is coming so don’t do it.
Thank you for the clarity Wayne. As I was watching I was thinking "If you hook up a 2 Ohm load to a 120V circuit, doesn't that mean 60 Amps go across those 28g test lead wires?". Dustin is brilliant, I think this one just slipped past him.
Thanks for the clear explanation! We had a fluke blow up on a tech about ten years ago and now only use cat iv meters and always kinda wondered what happened. He was checking a 480 feeder circuit, so I guess the circuit has a transient voltage come through.
I had a Fluke meter meltdown about 7 or 8 years ago testing electrical system in an elevator equipment room it was a rated for a thousand amps what went wrong I'm still not sure to this day one minute I'm standing there with a clamp meter in my hand the next minute is flames shooting out the meter and knocked across the room
I noticed at 6:40 you had the leads in the current measurement. A top tip especially for the young people, if you’re going to store your meter with the leads in it, put the leads in the voltage measurement configuration because that way if you aren’t paying attention before you use the meter you don’t short the circuit and damage the current shunt, pop your fuse, and possibly destroy your meter.
Imagine being an electrician and not being intelligent enough to turn off your meter so that it doesn't matter what you have it turned to. Also, even if you DID have the meter left on in the amps setting, you aren't able to put enough current down your leads off a 9V battery to pop your fuse anyway. Learn a thing or two about electrical work before you comment such bad info, teenager.
Electricians should be using cat 4 meters because we handle testing all the way to the service. He's right that the category number has to do with the environment you are testing. Think levels of protection. Electronics and power limited circuits are category 1. Category 2 would be after sub panels. Category 3 is protected by a main level panel. Category 4 is your service. In most homes electricians will only be testing in category 3 and 4 situations hence an electrician needing a meter rated at least category 4 600v. Industrial electricians may need a higher voltage rating but most commercial and residential work does not exceed 600v.
@@ChicaneMedia probably at least a category 2 but I would recommend a Category 3 because sometimes you'll want to use it on your electrical outlets if the tools aren't aorking. Category 1 is power limited electronics. Your best bet is to look at the available fault current for the car's power generation system, then check with the certification agencies as to what the testing requirements are for each category at the voltage rating you intend to get.
I hope nobody tries to use a light bulb as a multimeter now, especially if they connect it as a dead short like the picture 🤣 Great video and explanation, hopefully it helps some people understand their meter and the importance of the correct selection
Meters save lives. Any time I opened something up I checked for voltage, breaker is open, locked and tagged out, the switch on the wall is open, and there was still 115VAC present. The local switch was labeled with the wrong panel, but the panel was labeled for that circuit so the panel was labeled improperly also. And the local switch was wired backwards, breaking the white wire, instead of the black wire!
Good info. I was amused by your illustrators light bulb illustration at 5:00 where the leads were connected in a dead short across the ground terminal!😁
My EE background makes me call out some of this info, and in researching it, I found even more. First, what's with this "2Ω of impedance" on a CAT 3 meter? It's certainly not the input impedance of the meter in voltage measuring mode; putting that across 120V would definitely be noticed, as it would (try to) pull 60A through the meter. (Also, Klein proclaims the input impedance in V mode as 50MΩ, but the specs in the manual say 10MΩ.) 2Ω is pretty high for current measuring; on a 1A draw, it would drop 2V. Quite a lot on a 12VDC circuit. On the plus side, the Klein MM450 looks pretty sweet.
This was not clear in the video, but I believe the impedance numbers stated are those in the wiring from the service to the point of measurement. Thus I think the stated impedance is what will limit the initial short circuit current. Thus I belive a higher cat rated meter is designed to be used in a circuit that has a higher instant short circuit current capability.
@@noiseismymiddlename5669 Yes. The impedance mentioned is the SOURCE impedance not the meter's input impedance. The transient source current would then be equal to the maximum transient voltage spike divided by the source impedance. The lower the source impedance the greater the potential current spike at a given transient voltage.
Super important to note! a lot of meters (even some mid-range brands) do not actually meet their CAT ratings! The eevblog forum maintains a list of meters that do not meet their rating and I'm sure if you do some searching you can find out about any meter you are looking at buying. If I remember correctly Dave Jones got a nasty burn on his hand because a meter exploded while holding it. He wasn't doing anything wrong, but the meter didn't meet its spec and when it failed the plastic case wasn't designed to contain the explosion properly. If you are using test equipment daily then you need to demand the safest possible. If you see a meter have a glass fuse in it then it is very not safe; all meters should have ceramic HRC fuses that resist fragmentation.
Great video, when I was an apprentice my mentor taught me about the CAT levels and the importance of checking each meter prior to using it. This included the checking of batteries and fuses.
That poor light bulb..... Great video even for someone like me who's not an electrician but does the usual homeowner stuff like replacing the occasional switch, outlet, light fixture, etc as well as tinker with other electronics that sometimes deals with mains (or sometimes higher) power. My go to meter is a Fluke 87v which is admittedly overkill for anything I'll probably ever do but can handle just about anything I'll ever throw at it. Before finding a good deal on the 87v I found my Extech 330 to be a good meter for general home use and is Cat III 600V rated. Also recently picked up a Uni-t UT208B clamp meter which so far I'm impressed with but would go with a better brand if I relied on it for my day job.
Great explination of "more current at the source" Shorting a car battery is worse than shorting the wires of the break light. BTW - just a heads up. any metal connected to buss bars at 4MW and above makes a great flash telling everyone where you are (and what was done) Saw a OSHA documentary where the guy used a CAT-III meter on the HV side of a step down transformer. He did not die but suffered and bleed out for hours as they tried to save him. Not all deaths are quick and painless. Question - 2 ohms. At 600V two ohms is pretty low and would allow a lot of current to flow. The impedance is for true RMS and spike resolution on switch mode power supplies - right ?
Great tutorial. I would love to see some armored leads for industrial use. Something with geek strain reliefs at both ends and a Kevlar over-braid wrap with silicone jacket under it.
Can you make a video lesson explaining what is "available fault current" giving a bunch of examples. All DVM METERS have a "10 Meg ohm input impedance" so I'm confused why CAT 2 = 12 ohms impedance and CAT 3/4 = 2 OHMS impedance, can you explain this?
You are correct about the input impedance of the meter, at least in voltage mode. I believe he is Mis informed about this. I have an explanation of category ratings in the comment section that could be helpful. Also current rating of most DMM when in current mode are usually max 10Amps. So clearly current capability has nothing to do with the category rating. Where I think he may be getting it from is a robust input protection when activated can shunt the transient voltage through higher current rated components(ie. resistors, MOVs and alike) effectively shunting and discharging the energy. These components need to be more robust in higher category rated areas and therefore higher rated category meters have these higher Power components.
Been doing electrical work since I was about 11 or 12 years old helping out, learning how to use multimeters etc. Have in the past used it for measuring voltages at panels, and for verifying correct wiring at dryer and range receptacles, never knew about CAT ratings back then. 5 years ago I had an osha 10 class, as well as NFPA 70E. A real eye opener. Learned about a case where a maintenance worker was taking voltage measurements in on a 480 volt switchgear, when the meter exploded. Technician survived, but wished he hadn't, was very gruesome and that could've been me. Going forward, I always verify the CAT rating of the meter to the location as if my life depends on it, because otherwise I'm rolling the dice.
1:04 - you mention that if the two mains were to short it would allow a lot of current to flow due to very low impedance. Makes sense. But how much current would flow if you shorted or touched the two main wires coming from the transformer? Just curious.
I know you promote Klein products on this channel, but I have to say the very best price/performance multimeter I have ever used is the Extech EX570. Available from their website for $250, it is very fast and has very high accuracy. It is up there in accuracy with Fluke's which are 3x the price. Even Klein's best and most expensive are nowhere close to the level of the EX570
When you say 30 ohms or 2 ohms for those meters, are you talking about when used as an amp-meter or ohm-meter? Because typical ratings for a volt-meter are very high, on the order of 10 million ohms. The old analog meters were 10 - 50 thousand ohms. When used as an amp-meter, the impedance should be as close to 0 as possible. When used as an ohm-meter, the internal resistance should be relatively low, but the internal resistance of the meter is known and accounted for internally to get the measurement. When used as a volt-meter, the internal resistance should be as high as possible. When you stick a volt-meter across a circuit, you want to draw as little current as possible through that meter. The more current flowing through the meter, the less accurate the voltage reading will be, because the voltage drop in the circuit before it gets to the meter will be higher. Think about it using Ohm's law. If you used a volt-meter to measure 240v at the panel, and the internal resistance of the meter were only 2 ohms, you would be drawing 120 amps as soon as you connected the leads. Can you say *arc-flash event?* Obviously that's not practical. I was left confused by your video, so I decided to look it up and found this: www.digikey.com/en/blog/what-are-multimeter-cat-safety-ratings It turns out the impedance you're talking about is the impedance of the _test source,_ that is the impedance of the circuit being tested, not the meter. That makes a lot more sense.
I killed my Fluke when I tried to test for Voltage on a doggie 'invisible fence'. Apparently, they have HUGE current or voltage. Couldn't measure after that, so... couldn't tell.
Measuring electrical things can get complicated extremely quickly. Multimeters are also pretty limited in what they can actually measure, mostly because the display only updates say every half second or so (even 10 times a second is often too slow if dealing with electronics or especially digital logic circuits like computers or the like). An "invisible fence" (the kind that activates a collar on the dog, not the kind that has a wire that you get shocked if you touch it) shouldn't have blown out your meter, I don't think. At least, not the part you bury in the ground. They basically use a low frequency RF field (as in maybe 20 kilohertz, way below the AM radio band) of relatively low intensity, the low frequency is used because the wire needs to be buried and water absorbs higher frequency radio waves better than lower frequency radio waves (water is nearly always in good dirt especially if there is grass growing in that dirt), and the collar is what either delivers an electric shock or a tone or these days usually both. The only thing I can think might have happened is that somehow you had a resonant RF circuit created, and you tested the wire at the point of maximum signal amplitude. That might indeed cause a higher than expected voltage, but it still shouldn't be high enough to blow out anything. The only problem is that your meter doesn't update quick enough to be able to read out what the voltage is, since it's designed to measure 50/60hz AC and not 20khz signals. Some meters do have a frequency counter on them tho, this might be more useful, tho again you have to test in the right spot if it's a resonant circuit (the wire loop outdoors essentially creates a giant loop antenna, sort of like the loops that would interface with hearing aids that had a compatible reception coil, in places like movie theaters and stadiums). So I don't know why that would have fried your meter, unless you were trying to measure the shock output of the collar. That WILL fry the meter for certain, the circuit protection stuff in the meter probably can't react fast enough to save itself. For measuring that, you need an HV probe and a Digital Storage Oscilloscope, because again you're dealing with a high frequency signal (even if it only generates a single shock, it doesn't last for that long so the characteristic frequency is quite high), and the DSO will be able to characterize that waveform, while the HV probe (essentially a carefully calibrated series-parallel resistor based voltage dropper with a high voltage attenuation ratio and special HV resistors that won't arc over) will protect your measurement equipment from the harmful voltages.
Why is the Wire from Meter to the Circuit breaker box ALUMINUM? You would think it should be copper and have less impedance ? While testing ALL the circuits , the wires are Copper, not these though !
My last house had aluminum conductors to the panel and copper in the circuits. Nothing wrong with that. The electric company can do anything it wants. Like an idiot I had an electrician change it out to copper. Not needed.
@@Jnglfvr the smaller the better, i only ever use 2/0 copper from the meterbase to panel, alluminum is twice as big and can really be a pain for electrical changes way down the road
Aluminum service cable is safe to use. About 40 years ago was on a fire job after I gave the homeowner the price he asked if I was going to use copper service cable. Told him that I never used copper service cable but he wanted it. Told him that it would cost $300 more. He called me a F'ing thieve. Cable was a $1 an inch. Guy must have got other quotes & called me up the next week to do the work. Told him to go F himself.
Both run 2 circuits in a single cable. 12-2-2 has 2 hots (black) and 2 neutrals (white). 12-3 has 2 hots (black & red) and share a neutral (white). A common use is in kitchens and dining rooms. By Nat. Elec. Code, both locations must have 2 20amp small appliance circuits. 12-2-2 can use 2 individual breakers. 12-3 must use a double pole or if using 2 individual breakers, the handles must be tied together (by today's code) to shut down both circuits to prevent back feed through the shared neutral. There is a segment on the issues created using 12-3 on this channel.
2nd year industrial electrical apprentice here and hoping someone can help. I’ve been told 277v “doesn’t have a neutral” and that’s why it’ll shock you when we work on lights. But how can a lighting circuit not have a neutral ? Could this be because there is a load on the neutral or maybe it’s sharing a neutral with another lighting circuit ? Thanks
@@waynecostanza2280 not sure. But always been told the neutral on a 277v circuit will always shock you and I have been shocked by it before. Im just not sure why a neutral would shock someone?
@@cyle_rado I’d guess bc when you start to take apart the neutral you can open it and creates a voltage? And 277v definitely contains a neutral. I’m kinda glad they’re moving away from 277 in non industrial buildings
in a commercial building, there is often a transformer for each floor, creating the Y 277/480; it's like a service, and creates/defines it's own independent neutral. It should always be bonded to a ground at the service point of entry (this might be inside the transfo, or main panel for that transfo; where ever the main service disconnect is located). All the plumbing & steel in the building should also be bonded to the same ground somehow... Also, you can get shocked of any neutral if it is carrying current for other circuits, or there's wiring errors, or other faults.
I would say this would make the most sense to me, just like a multi wire branch circuit that has two hot legs and a shared neutral, if you don’t correctly install a ganged breaker and you try to work on the neutral you can get shocked.
I've had an Simpson 260 for more than 20 years and served it's purpose. Also an amprobe to measure ac current. The VOM isn't auto rangeing but just start at highest voltage setting. Oh btw don't try to measure voltage on ohm settings, quick way to instant fry !!! Occasional digital multimeter for more accurate readings. Think these plug into outlet gadgets makes dumb electricians as Google maps makes dumb drivers. But what do I know,. am Old School, though do use G maps and getting dumber by the days 🙃.
Confusion on Cat III showing a rating of 1000V and Cat IV 600V on the meter shown. But yet you stated that Cat IV meter can be used at voltages over 600 volts. So why is the rating marked 600V?
You should not measure voltages over your meters rated voltage. Leads, terminals and internal construction is designed to have enough dielectric for its rated voltage. Applying 480v to a 300v meter could be very dangerous. It just isn’t made to withstand the electrical stress and could result in an arc or shock.
Not quite, the category environment dictates what category meter you need, the working system voltage dictates what voltage you need. For instance a Cat IV 300v is good for a 120/240 pad mount transformer located near a utility pole. However a 277/480 circuit off a three phase panel would need a Cat III 600v, this is because the line to line voltage would exceed the working voltage of a 300v meter. So the Cat rating is for transient over voltage due to the proximity to the source of energy and the voltage rating is for what voltage you will be working on.
PPE approved clothing tested & labeled in Cals. At the large company that I retired from we had CAL 9 &11 long sleeve shirts, pants, sweat shirts & winter jackets. If you own any PPE clothing NEVER use fabric softener while washing!
*Checks multimeter * both my multimeter and my clamp meter are CAT 3 / 4 and I'm a home owner not an electrician. To be fair the first fluke multimeter was stolen by my parents tree snaged it off a truck and they never returned for it.
You're welcome to review EEVBlog's channel where he goes over quite a few meters and their "Claimed greatness". ru-vid.com?search_query=eevblog+multimeter+shootout
