Re: Re: *muppet alert* How do I use my multimeter?

["Ian Lowe" <ian@xxxxxxx>]

One quick warning!!!

don't use a PP3. if you do have a short you will incinerate the thing...
especially if you clip it on then wander to the other end with a bulb!

Ian.
----- Original Message -----
From: <matthew@xxxxxxx>
To: <ukha_d@xxxxxxx>
Sent: Saturday, June 16, 2001 12:13 PM
Subject: [ukha_d] Re: *muppet alert* How do I use my multimeter?


> Thanks Keith. I've got to turn the power off in a mo to decommission
> the sockets in the room above node zero so when its off I'll test the
> wire again to see if it was induced voltage causing the problem (the
> wiring to be decommissioned runs next to the coax at the moment).
>
> If i still get funny readings I will hunt out a bulb and a battery
> from somewhere and try the low tech method.
>
> Cheers
>
> matt
>
> --- In ukha_d@y..., "Keith Doxey" <ukha@d...> wrote:
> > Either you are not making proper contact with the probes or you
may
> be
> > picking up some induced voltage.
> >
> > Resort to the low tech method.
> > Battery and bulb. Battery at one end, bulb at the other. If the
> bulb lights
> > OK then the cable is OK. If it flickers, (which it would do if
your
> 0.7 to
> > 170 reading is accurate) then the cable is knackered :-(
> >
> > Keith
> >
> > > -----Original Message-----
> > > From: matthew@m... [mailto:matthew@xxxxxxx...]
> > > Sent: 16 June 2001 11:07
> > > To: ukha_d@y...
> > > Subject: [ukha_d] Re: *muppet alert* How do I use my
multimeter?
> > >
> > >
> > > Ian
> > >
> > > Thanks for your help. I set the meter to 200 ohms and the
results
> are:
> > >
> > > 1) 1
> > >
> > > 2) Anything from 0.7 to 170!!!
> > >
> > > The meter is a digital one and for test 2 i would have
expected a
> > > constant readout? I'm not waving the cable around and the
prongs
> are
> > > firmly pressed down.
> > >
> > > Any comments?
> > >
> > > matt
> > > --- In ukha_d@y..., "Ian Lowe" <ian@w...>
wrote:
> > > > two quick tests matt:
> > > >
> > > > make sure both ends are "clean" (ie not
shorting together core
> and
> > > screen)
> > > >
> > > > Measure resistance between core and screen: if you get
a dead
> short
> > > > (anything up to about 15-20 ohms) then your cable has
stretched
> > > internally
> > > > and the core and screen are touching.
> > > >
> > > > then take one end and twist it together so the core and
screen
> are
> > > shorting:
> > > > go to the oter end and emasure: anthing *Except* a dead
short
> means
> > > your
> > > > cable has been damaged and one of the conductor paths
is broken.
> > > >
> > > > Ian.
> > > >
> > > > ----- Original Message -----
> > > > From: <matthew@m...>
> > > > To: <ukha_d@y...>
> > > > Sent: Saturday, June 16, 2001 10:36 AM
> > > > Subject: [ukha_d] *muppet alert* How do I use my
multimeter?
> > > >
> > > >
> > > > > Having put in quite a long run of coax from node
zero
> (garage) to
> > > the
> > > > > loft as the downlink from the aerial, I noticed
that about 12"
> > > from
> > > > > the ceiling of the garage it has gone a bit
floppy.
> > > > >
> > > > > Suspecting the coax may have broken inside
(bugger!) I've
> gone out
> > > > > and bought a cheapo multimeter.
> > > > >
> > > > > I've stripped the end in the loft, and twisted the
braided
> screen
> > > > > around the solid core. Back in the garage, the
options on my
> meter
> > > > > are 2000k, 200k, 20k, 2000 or 200 ohms. I guess
the plan is
> to set
> > > > > the meter to one of those, touch one prong on the
core and
> one on
> > > the
> > > > > screen and look at the value displayed.
> > > > >
> > > > > Trouble is I have no idea what I'm looking for. I
don't know
> what
> > > > > values will tell me the cable is broken and what
values will
> tell
> > > me
> > > > > im ok. I also have no idea what OHMs to set the
meter to.
> Assuming
> > > > > the cable isn't broken, is there some way I can
test the
> strength
> > > of
> > > > > signal ie. how much loss there is over the run?
I'm reckoning
> on
> > > four
> > > > > runs of coax from the loft to the garage and it's
CT100 cable
> but
> > > if
> > > > > the losses are too great I'll have to get some
CT125.
> > > > >
> > > > > Any help and advice gratefully listened to!
> > > > >
> > > > > Yours muppetationally
> > > > >
> > > > > matt
> > > > >
> > > > > (ps. I promise one day I will contribute something
worthwhile
> to
> > > this
> > > > > group rather than just ask questions all the
time!!!)
> > > > >
> > > > >
> > > > >
> > > > >
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