how do we test voltage and why do we need to
voltage is a relationship between two things when we are sensing voltage we're testing you can kind
of think of it as electrical pressure sort of it's a good analogy it's not 100 accurate but it's a
kind of a pressure that exists almost like when you take a slinky and you pull it apart imagine
being able to test the force at those two points so when you let them go the force comes together
in an electrical circuit current flows because there is pressure there's a potential we call
it a difference of potential it just means voltage but it's required that you know thing a and thing
B and what they are because sometimes in a circuit or in an environment there are multiple different
things that you could have voltage between and you need to know how much voltage you have
between everything in a three-phase environment you might have something that's a center-tapped
Delta where you've got 240 between all three of your different phases you know A and B's got 240
B and C's got 240 and CNA may have 240 but if you test between neutral or ground two B phase
it might show 208 you need to know that so that you don't start putting Breakers and loads single
phase loads on a 208 circuit because if you think it's 120 and you go to put your vacuum cleaner you
know plugged in you're gonna fry that thing so you need to know voltage between two things what
this is relative to this this this this and this so that's why it's really important to be able to
test for voltage now there are also things that should never have voltage between them and that's
really important too so we use a Multimeter that tests voltage between two things that should not
have voltage and if you ever get a service call or something because somebody is getting shocked
every time they touch this metal door frame you've got to start being able to test and know okay well
that's a metal thing that probably has something to do with grounding maybe a neutral so you're
always going to be testing multiple different places to see where is the pressure getting to
this where are Earth what is the potential what is at a different potential that's allowing current
to flow through it all right to start out let's talk about a couple of tool options a lot of
people use this thing this is a tick Tracer it's a non-contact voltage tester ncv so that means that
you don't have to make contact you can just sense when there's voltage and the thing will light up
this is not telling me anything about anything this is not telling me voltage it says that it's a
non-contact voltage tester well what's the voltage is it 120 is it 240 like how do we know so using
this thing is not actually accurate and look it's like reading way the hell out here because it uses
capacitance it doesn't use actual voltage it's not telling you that there's a difference of potential
between this thing and this thing so it can give you a reading between the two things voltage is
always a function of two different points and it's the potential between those points so this thing
just sitting here squealing at you every time I touch myself I don't have voltage but there is
capacitive coupling that's happening between me and another thing so it's just really inaccurate
and I tell people not to use these Because unless you know what capacitive coupling is and you know
actually how this thing works and what you're testing it's going to give you false positives
a lot of the time most people will come up here electricians and they'll go like this they'll be
like oh breakers on go turn the breaker off and that's what they're looking for for this thing to
stop making noise and it usually works it tells you if there's a presence of power but it is not
a voltage tester it is not actually telling you any voltage and it has voltage written all over
it every Brand's the same way it's not voltage that it is telling you so don't use this thing as
a voltage tester just understand it's used for the presence of power to tell you if things are on or
off but I always always because this thing is is just not as reliable and it's not actually giving
me any information I always come over here and I grab a multimeter and I want to use a Multimeter
to double check everything before just trusting this little tick Tracer now another thing I want
to talk about is using one of these so this is a plug tester this does not tell you voltage either
this will tell me that the receptacle is hot sure it tells me that it's wired correctly that
you know everything's wired as it should it'll also tell me if things are swapped backwards but
without using this how do I know if the white has got voltage on it or not right so you can't use
this for voltage either this is just a plug tester just letting you know the presence of
power is there it's kind of an on or off thing and it'll also help you to let you know if you
wired it forwards backwards so I actually use these quite a bit but not to tell me voltage and
I need to know voltage as an electrician voltage matters more to me one thing that recently came
out is these little buggers so Klein developed a plug tester it's the same thing as the last one
it just actually gives you voltage values which is really cool look at that tells me 125 volts that
it's wired correctly it'll let me know if there's a problem if things are wired incorrectly you can
test just like if it's a GFCI if you've got a GFCI somewhere you can hit test and it'll trip it like
the other one had I just didn't talk about it but it's good it gives you some kind of information
as an electrician we need no voltage we need to know that information so let's talk about
how you actually test for voltage though because not everything's a receptacle you know the only
downside of this thing is that it only works on receptacles but if we're testing in a panel where
we're testing a receptacle and we actually want to know what's the voltage between this thing
and this other thing right so we know here between hot or black and between white we should have 120
volts and we do 125 I'm in a commercial setting so my voltage is a little bit higher to this building
but also we have 120 volts between ground and hot too so I left my hot there now between ground I
should have 125 and I do so like cool now I know everything what it is relative to everything else
when we're testing voltage we're trying to say essentially what's the pressure between these
two things if we go between neutral and ground it should show zero volts there shouldn't be
any pressure pressure that can allow current to flow between the neutral and the ground because
they're bonded together out at the service we don't want there to be a difference of potential
and that's all voltages is difference of potential so it's telling us between two things so let's
look up here uh I have this wired in a crazy like uh crazy way just for like demonstration purposes
right now there's no incoming conductors here because they're being fed through an extension
cord uh into these Breakers the breakers are then feeding power to all of these little teeth
which makes the whole entire thing energized so it allows me to get power up here as well
so I have this wired and it's not 220. I only have an extension cord that's got a black and
a white and a green so right here you would think oh between each one of these I should have 220 or
240 and I don't so this is giving me information say out in the field we lost a phase or something
like that and you're not getting 240 between a phase and B phase or you know maybe this is
a little bit easier for you to see there's no voltage between here well damn okay what about
the neutral oh holy crap there's 125 volts between hot and neutral what about the other hot neutral
there's still 125 volts hmm that's really weird we didn't have anything here though
well it's because both of these are being fed right our hot is coming in it's plugged into a
wall it's jumped over here so both of these Hots are hot they're just at the same potential because
they're both touching each other so this hot to neutral is reading 125 and this other phase which
is our B phase up here is also reading 125. so both of them have 125 volts of potential between
ground and hop but they don't have any potential between the two of them because they're both at
the same potential it's literally they're touching each other it's the same exact thing so then we
could go okay well what about you know neutral to ground or what about a hot to ground we should
get same thing right 125 volts between a hot and a ground and we should get nothing between our
ground and our neutral and it shows zero volts because again grounds and neutrals all the way
out at the service are actually bonded together there's a little either a wire jumper that goes
between them or a lot of times there's a screw like this one has and we'll put that screw right
in this hole and we smash it through and that takes all of our neutrals and it touches them
to this metal can and this metal can is touching this ground bus so ground panel metal and neutral
are all touching each other because we use this bonding screw to bond at all we only do that at
the service we don't ever do it in an inside panel like this but it just goes to show you
since the the all of the neutrals and the panel and the ground are at the same exact potential
they're all one giant piece of metal so why would there be a difference of potential between them
there isn't because they're the same piece of metal that's why you're going to get no voltage
between ground and neutral now if you're ever on a job and you do have voltage between ground and
neutral then you have a grounding problem them or a neutral problem and you need to go investigate
that because somebody could actually get shocked and it's really dangerous but that is voltage so
you can understand now why a tester gives you values it gives you numbers because you're
trying to see well does this have voltage between this is their voltage between this and this using
this thing to sit here and just beep at you look it just beeps no matter what you touch I don't
even have to touch anything I'm just near all of this what is this telling you it does it next to
the neutral sometimes it does it well it doesn't do it on the ground but it's there's no useful
information here so only use this for the presence of power sorry I should probably shut that off
while I'm talking to you or use it because it's got a cool laser on it and if you're a juryman
and you're telling people what to do you can shoot it across the wall and you'll be like hey go run
in between here run a little box or go like go make those wire nuts up right there that's the
reason I use this thing but if you're testing voltage use this thing go spend the hundred
dollars keep one in your garage and use it every time you ever mess with electricity but I'm gonna
recommend as an electrician you hire me instead and don't mess with electricity so that is voltage
thank you guys so much for watching I love you crazy people and I will see you in the next one