so let's do a little bit of multimeter
101 because this is a tool everybody
needs to use for any kind of board level
diagnosis so let's kind of talk about a
little bit because I think it's
intimidating you know where you're like
I see a whole bunch of hieroglyphics and
I have no idea you know like this this
you know a lot of them have these two
sort of symbols for voltage one is V
with a straight line and one is V with a
wavy line now I know you know the
multimeter so what does that mean to you
like what do you what do you think when
you see V wavy line and V streamers so I
think ACDC yeah me too I think heavy
metal so the V with the wave is
alternating current you know which is
what comes out of your you know your
house electrical lines and then the V
with a straight line direct current DC
and that's the kind of current that is a
battery powered by any insight any
electronics you have your power brick
here and your power brick is converting
from a CD so once you get to the device
we're dealing completely in DC right so
another way you could say to kind of
make things simple is if you're trying
to troubleshoot electronics ignore
anything you can just put a big sticker
over anything that has to do with the V
wavy line so that's out of the picture
so then let's talk about the V with a
with the straight line so DC voltage
measurements so what is voltage what do
you think of when you think about
voltage I think of potential energy
that's a little nerdy go I this takes me
back to my physics class right you have
if I have this and I lift it up yeah
okay it's got more in there I added
energy to it yeah if it drops it's going
up with more energy yep so a battery is
storing energy
yes dead battery it's like this sitting
on the table if it's charged it's like
it's sitting up yes so I was thinking
about this earlier earlier today because
you know I was thinking like how do you
sort of make this you know simple and I
and I think you know like let's take
sort of an analogy of me trying to like
blow air through a straw like to blow
bubbles in some chocolate mouth or
something like that so the actual like
power to blow and move that
err that power is voltage you know it's
sort of like you know it is potential
energy it's the same thing sort of like
the the pressure to drive something from
A to B no energy potential energy
voltage so we need to have voltage in
order to push electrons through wires so
then while we're talking about the the
multimeter the other things that we kind
of need to understand other than volts
volts is you know the power the pressure
to drive the electrons through through
the the wires the other thing would be
the a so the a stands for amperage
amperage so what do you think about with
amperage so in your analogy amperages
the air so you have the force behind the
air amperage is the electrons flowing
through the wire exactly so movement and
I think of it as sort of like a like a
you know it's a velocity it's a miles
per hour it's you know I could blow ten
bubbles per minute you know it's
something that has sort of a rate you
know and amperage has far more they do
with the size wire you want to use that
voltage does yeah so it's how many
electrons can you fit through so you
have a big wire like you'd have in the
house that's gonna be running a lot of
electrons through it right and so the
size of the wire is the resistance so
that's the last piece of the puzzle so
the ohms is the is the resistance now
it's really difficult to measure and I
tried to explain this in practical board
repair school as well it's really
difficult to measure that flow the rate
the the current you know the the river
of electricity running through the wire
it's impossible really to measure that
without sticking your finger in the wire
does that make sense you know to
actually feel those electrons flowing
through there you have to have a probe
inside the inside the wire and we and we
can't really do that and so the circuit
board can't really do that as well but
we can infer what the amperage is if we
know the other two pieces of Ohm's law
so if we know the voltage and we know
the resistance so we're not gonna get
too much in the math but this is now
equals IR so if you measure the voltage
and you measure the resistance you can
calculate I which confusingly is current
for amperage I know and I you know I
really love to just talk about it in
ohms resistance amps and volts you know
so at the end of the day here's what's
important you need to be a real
measured voltage because that's the
power driving the flow you don't really
need to think about the flow at all
you're never gonna measure it because
it's hard to measure right you don't
need to think about AC because that
doesn't have any things it was
electronic so all you really need to
know is voltage is you know measuring
your power and resistance which is
measuring you know how hard it is how
big or narrow the wire is you know how
much impedance resistance there is to
the flow of electrons and so different
components on the board are put there to
restrict or allow the flow of electrons
and they'll all have a certain
resistance that we'll need to measure so