Ok, we are going to take a look at doing some testing with a Fluke 88 meter
actually this meter is a V model which is just slightly above the normal
88 meter. The first thing we need to do is make sure we have the meter leads in
the correct jack positions for doing voltage testing.
Okay so we have the red jack in the volts scale.
The first thing we're going to do is check the voltage for the
available power source we're going to be using in this particular video.
The other one is connected the black one in the common jack
so that we have two leads that we can make in connection to parallel to the source voltage.
Ok so now we need to select the correct
range on the meter for what we're testing. We are going to be testing
DC voltage and the available power source that we do have
the very first one on the scale here is AC voltage that shows that sine wave
for AC voltage. The next one above it
is for DC voltage with this straight line with the hatch below it
so I'm going to rotate the meter to that position
and you can see on this scale here when we illuminate it
that there is nothing on here as of yet. W hen we make the connection to the power source
then we will actually be able to read the value and we will come back and take a look at that.
S o we have a power supply here it's connected to AC voltage
and then it converts it to DC voltage that we're going to be using for power supply
in this particular test. I'm not sure exactly how much is here but we need to
know the value if we are doing
Ohm's Law calculations when we start placing
resistors into the breadboard. So very first thing I've done is I
clipped out the red onto the wire so we don't have any arcing or
sparking or any potential for melting any wires.
So all I am going to do is I'm going to take my red lead
make the connection to the volt meter lead and then the black lead
and make it to the black lead on the volt meter and then we're going to take a look at it
on the volt meter for the value that we have for the available power source.
So you can see here now on the display
that we have 14.42 volts
coming from this power supply so we need to take note of that
that that's the available power source that we have in this particular circuit
so when we start doing calculations and looking at voltage drops in the circuit
the series circuit that we are going to look at that it all is going
add up to the available voltage when we drop
accordingly across each resistor.
So taking a look at a project breadboard and this is
something that's typically used with electronics for laying out circuits and
establishing how the circuits gonna function for testing this circuit
testing different components making different things
function based on where you put them on this board.
So there's different quadrants on these boards
some go in this direction and some go in this direction
So anytime we look at the ones going across here
we're going to be in series. When we start putting
loads from this quadrant to this quadrant
then we are actually going to be in parallel.
So I have selected a couple of different resistors
in other videos there's an explanation on how we define
the resistance value based on the color coding thats on the resistor.
At this particular point what we're going to do is go in and do a physical
measurement of the values and then do the calculations for voltage drops
across a series circuit. So all I am going to do is gonna take these resistors apart
and I'm gonna start to lay them
out in a series circuit in the board. I am going to start in one quadrant
and I'm gonna jump to the next
and I'm gonna take another resistor and I have to be in the same
row to make the connection
So I am gonna pick the next quadrant below it
and then I am going to move and pick another spot in series.
Now have some other resistors
and again I don't know the values but I'm gonna take those resistors
and again I have to come back down and pick the same row so I have the
same connection
a bus connection any time we talk about a bus connection
it means that there are multiple places that connectors or conductors can be
fastened to transfer power
or ground. So I'm gonna continue on placing these
along and we will just start with 3
in series and as you can see the power would flow from this one
through this one, through that quadrant, through the next one
through next quadrant, through the next one to the end of the circuit which shows that
we have a series
of resistors connected together.
So we're gonna go in now and we're gonna check the resistance of the series
of resistors that we've placed in the breadboard
and now we have to make sure that our jacks are in the right position
for doing the resistance check so we have the black jack in the common
the red and again on the meter it shows we can check voltage
ohms, diodes and RPM so we're in the appropriate position
for testing now we need to take a look at the
position of the dial to put it on the right scale
for checking the resistance of the resisters that we put
in the circuit so now we're going to do is we're gonna turn the dial on the
meter to the correct scale
and we want to be on the ohms scale so we're just gonna rotate it
to that position then we can go back to our bread board and check the
resistance value of
each resistor that we have
placed in that breadboard.
So we are gonna go ahead and make our connection now and we're gonna test the very first resistor
and we're gonna look at the value of that particular resistor.
So we're gonna check the second one and read the value.
We're gonna check the third one and read the value.
So now that we've measured all the individual resistance value we're going
to calculate out the resistance
total in the circuit and in a series circuit the resistance
total is based on the sum of all individual resistance values
added together so I'm going to calculate these out
468 plus the 470
plus the 218 ohms calculates out to 1156 ohms
So now we're going to take a look at this and actually measure it
in the series circuit. The overall circuit resistance
should calculate out to 1156 ohms
on the meter meter.
So at first we went we measured each and every individual resistance value
and to get the overall circuit resistance we added them up
and the value I came up with the was 1156 ohms
So now I'm gonna make my connection over
the entire circuit and then I am going to look at the value and see if it adds up to the
calculated value
of all individual resistance values.
So now what I'm gonna do as measured earlier in this video
we had our available power source so all I'm gonna do is make my connection
at one end
and make my connection at the other end and as you can see the power flows from
the power supply unit through the first resistor
through the next resistor through the next resistor
and back to the source voltage so what we're goin g to take a look at now is
based upon the resistance value in this series circuit
we're gonna drop a certain amount of voltage based upon the resistance in
each particular component
in this series path.
So remembering that we are on the ohms scale, we do not wanna
connect or cook the ohm meter by connecting it to a live circuit
so we need to make sure prior to doing any testing on a live circuit that we move
offer the ohms scale and go back to the scale we are looking for
which is DC voltage. So one thing when you're working with bread boards and you
have an AC to DC rectified power transformer
to actually give us our power supply here if the circuit takes some time
to measure and calculate it's always important to go back
and check and recheck your source voltage
because based on the heat of operation of that transformer
it can actually change the output voltage slightly so I'm gonna double check
what my source voltage is since we have started
beginning in this video. So I will make my connection
and check the value.
So the value has changed slightly from what we started with and now we're at 13.31 volts.
It's actually changed since I did this measurement
so this power transformer
is obviously changing consistently as we continue through
we have 13.31, 13.30
and it may even drop back down to 13.29
So I'm gonna take the connection off, put it back on just double check
and this one is showing now 13.30 volts.
So now we're going to make the connection
from the positive power and we're gonna go across the very first resistor
and then read how much it drops based on the resistance in this particular resistor.
So the voltage drop on the very first resistor
as per connection is 5.38 volts
The next one that we've checked is 5.40 volts.
and the last one that we've checked here works out to 2.51 volts.
so what I'm gonna do now is take the values of the voltage drops
that I have already recorded
and I'm gonna add them up.
So 5.38 volts plus 5.40 volts
plus 2.51 volts
The total on this should equal 13.29 volts
which means we've dropped in direct proportion to the resistance
in this series circuit so whatever we start with
we should end with as far as the voltage. So we started with 13.29 through measurement
and we calculated out to 13.29 in measurement
and again you seen on the display
that it varies slightly and through explanation
of the change of the voltage with the transformer.
So one of the circuit characteristics of a series circuit is that the
sum of all individual voltage drops will equal source voltage
so as through calculation and measurement
the voltage dropped in direct proportion to the resistance
and actually equalled source voltage.