so in this presentation we're going to look at setting up our Megger mft
in order to carry out either a continuity test or an insulation resistance test
we know our instrument needs to be calibrated every 12 months and this one is in calibration
date however as we move and extend our learning we should remember that this instrument needs to be
checked by the user and it should be checked every month for all the tests that you can
carry out to prove ongoing accuracy there's no point just sending it away once every 12 months
you drop it the minute you get it back and all of a sudden your readings are no longer
within tolerance so we've got the Megger mft check box here and in a later presentation i'll
show you how we set up that in order to check our instrument over an extended period of time they
even issue you with paperwork to allow you record your monthly results for both live and dead tests
so we will be showing that in another presentation this one's concerned with our early stages of
learning which is setting up our Megger mft which is in date for calibration in order to carry out a
continuity test and an insulation resistance test let's see how we're going to do that so we select
our test instrument in this case our Megger mft and we need to confirm that it is in date today's
date is the 18th of december 2017 and as we look at the sticker here we can see is within date
that doesn't prove that the instrument would give me accurate readings and as we said at
the start of the presentation you will need to do monthly checks to prove ongoing accuracy of
your instrument which i'll cover in a later presentation at the moment we're looking at
basically setting up for a continuity test or an insulation resistance test and that's about where
my learners are as we approach Christmas so okay now we've got our Megger mft out we've proved that
it's got a valid test certificate against it so we know it's been calibrated by the manufacturer
so what else have we got in the box we've got a series of leads and probes so we've got blue red
green including the probe tips for all three as well as the crocodile clips for all three as well
as our plug-in test lead for when we're doing ring final circuits or radial socket circuits as well
these all need to be inspected so we're looking to check the leads check there's no nicks
no damage no splits and they're in good working order so all of these need checking including
the plug top itself and leads here so we have a once over
just to check the insulation hasn't been damaged and we have any broken ends etc
then we're ready to start removing the resistance or proving continuity of the leads before we
actually carry out any of our dead tests so with everything present and checked lead wise we can
now turn on our instrument onto the orange ohm scale and we can see once it's turned itself on
that it will actually give us a battery indicator here in the top corner and we're looking for that
not to be flashing and there to be enough bars to suggest the battery is good if the batteries need
replacing it's a simple case of undoing these two screws and inserting six AA batteries in
replacement of the ones that are already there our battery is good so we're ready now to work
out whether we'll be carrying out a continuity test or an insulation resistance test and checking
our leads are up to carrying out that task so for carrying out a continuity test i'm going to
need to use the red and green hold sections in the top of my Megger mft it doesn't matter if we use
the blue lead but we must use the red and green holes however logic says we're going to have a
red lead and a green lead in here for carrying out continuity the blue one here is only used during
the live testing of which the continuity CPC is a dead test so we're going to set our instrument up
it's already set to ohms we're going to have to remove the resistance of the leads before
carrying out the tests and we're going to use the red and green lead so let's see how we're going
to remove the resistance of the leads before carrying out our continuity test let's take
our red and green probes let's push them firmly into the holes in the top of the test instrument
and then we're ready to remove the resistance that will be offered by the leads themselves
okay taking our fingers squeeze them firmly together it's quite difficult very small
tips squeeze them firmly together and we have a reading in this case of zero if it wasn't zero
let's press the test button once we've got 0.07 press the test button and it zeros out
the resistance offered by the leads themselves so we're at zero those leads now are ready to go off
and carry out the continuity CPC test in circuit but we could have used the crocodile clip so let's
see how we would zero the leads if we had the crocodile clips on so let's change the probe tips
now for crocodile style ones so take those off and insert on the crocodile ones i like the fact that
this part here lifts up so when i press the button this lifts up i like to use the bottom section
for zeroing my lead so i use the solid part not the hinge part so i go solid to solid
like so i just squeeze them together just leave a little squeeze and we'll look at the reading again
we're already at zero which is handy but if i press the test button once you'll see we have a
reading if i press the test button again you can see that we've removed the resistance of those
leads so just to reiterate i don't like the hinge section here i like to use the solid part of the
belt on the base so that moves up so i tend to use the bottom part here to here maximum surface area
to maximum surface area and then we check our instrument and we can see that we've zeroed out
the leads now with the crocodile clips connected and finally let's remove the resistance of the
lead when we have one probe and one crocodile clip separate these off put on my probe again
i lift the hinge up and i like to probe it on against the solid part in this case at the base
let's just hold my hands that way worst bit and again for some reason i've already got zero but
let's press the test button once we see we have a reading press the test button again it's zero zero
zero it's not flashing so it's not below zero and we'll remove the resistance of the leads this time
with one crocodile clip and one test probe so again we're ready to carry out a continuity test
when carrying out a continuity test on a socket circuit we're likely to be using the socket
adapter lead within our Megger mft box we are going to need to remove the resistance of these
and we in both cases whether you're testing a ring final circuit or a radial socket circuit
we actually test between line and neutral first so we're going to need to use
the red and blue leads and remove their resistance as part polarity during that test
and as stated before we're definitely going to have to use the red and green sections in the top
of the Megger mft because it's a continuity test blue one i'm going to put into the green section
and the red in the red section and we now need to remove the resistance of this lead so we need to
short together the line and neutral pin here previous presentation i showed you using
a knife you could use a crocodile clip you could use a coin or something metallic
so i short those two pins together i see we have a reading of 0.07 press the test button once
and i've removed the resistance of the line and neutral for a continuity test in this case it's
part polarity the continuous CPC requires us to move the leads across so that's testing
between line and neutral to complete any test on a socket circuit we need to test between
line and circuit protective conductor so i swap my leads over now and i now need to remove the
resistance when carrying this part of the test between the line pin and the earth pin
so link those two together once again we've got zero but if i was press the test button once we
have a reading if i press it again we've zeroed out the leads itself and we're now ready to test
between the other two conductors i've stated in two previous presentations ring final circuit
and radial socket circuit testing why we're doing both of those but that shows you how to zero out
our longer lead with a plug top on it during the continuity tests so next one to zero out would be
if we were using a long wandering lead it could be that we are testing the protective bonding
conductors continuity or we're just doing an r2 test at different points in the circuit i've fully
unwound this off camera and checked that there are no nicks and splits in it but for the presentation
purposes i've wound it back up because obviously trying to get it on the desk is quite tricky
there's a huge amount of cable here there's 50 meters so all of that will need to be removed
i've put my probe into the side here so i'm using my green lead so it's into the side
of the wandering lead and we've got the probe connection that comes with the actual wandering
lead itself which will go in this case into the green section the top of the Megger mft
and as always we'll use the red one in the other hole so exactly the same as previously
stated and again we've got two crocodile clips so i want the maximum surface area to maximum
surface area in that position a little squeeze and we see we've got a reading this time of 0.93
press the test button once press the test button again so this time we've now gone down to zero so
i've zeroed out that 50 meter long lead allowing me to go off to do R2 testing or continuity of a
protective bonding conductor so now we're going to set up for an insulation resistance test
we're going to set our instruments around to 500 volts DC in the megohms scale we're only testing
either a 230 volts or a 400 volt circuit here at college we're going to use once again the green
and red sections in the top of the Megger mft but i'm still going to short my leads together okay
so i'm going to short these together in order to prove i have a dead short so once again i'm going
to use the crocodile clips maximum surface area to maximum surface area on the non-hinge section
and i'm going to see if i get a dead short so press and hold the test button this time
and i have zero zero zero have a dead short so what i've now proved is that these leads
haven't become broken in any way they were broken so we just disconnect them
and we were to have the insulation resistance test done again we can see we've got a reading greater
than 999 megohms which we think is fantastic when testing but it might be the leads themselves of
you know snapdragon become disconnected where we can't see it actually within the mechanism
of the say the shaft or at the end here where we put the probe into the top of the test instrument
so once again maximum surface area to maximum surface area and we're going to press and hold
our test button and see that we have a dead short before carrying out our insulation resistance test
so that's showing us once again how to set up to do dead tests whether we're doing a continuity
test or whether we're doing an insulation resistance test so we confirmed our instrument was
correctly within calibration date we confirmed our leads were in good working order before starting
we removed the resistance of the leads for continuity testing and we proved they weren't
broken for our insulation resistance test in a later presentation we'll look at the check box
and the need for ongoing accuracy tests every month in order to prove our in this case Megger
mft is in good working order and giving results that are correct i hope this has been some help