If you're doing anything with hardware, you're going to want
a multimeter.
But before you start poking around with power, make sure
you know what you're doing.
You don't want to run into any problems where you have
electrocuted yourself accidentally.
So be sure that you've trained and know exactly how to use
these multimeters in your environment.
These multimeters do so much for us.
They can measure voltage, and current, and resistance.
You'll sometimes see them referred to as a VOM.
That stands for a Volt-ohm meter.
There are analog versions, there's digital versions, and
all of them are pretty inexpensive.
The accuracy will vary widely, though.
There are some multimeters you can buy for thousands of
dollars, or you can buy one for less than $10.
You just want to make sure that you have the right kind
of multimeter for what you're trying to do.
Whenever I'm looking at a multimeter, I want one that is
very clear, relatively easy for me to use.
I'm not looking for a huge amount of accuracy,and I think
my multimeter, which is shown here, probably
cost me about $20.
And that's about right for the type of work that I do with my
computers and the type of things that I need from a
multimeter.
Multimeters are great for checking
things like AC voltage.
That alternating current that's coming right out of
your connection in the wall can tell us what type of
voltages we have to be seeing so we can validate that we're
getting exactly the right kind of power for the power supply
that's inside of our computer.
Once our power supply is converting things to direct
current, we can check those voltages as well with our
multimeter, check the motherboard, check to see if
your CMOS battery has enough charge inside of it to
maintain the configuration of your computer.
All that can be done by checking the DC voltage.
Continuity checks to be useful as well.
You can check fuses, you can check to be sure the cables
are connected from one end to the other.
Multimeters usually have also a beeping sound you can turn
on, so not only are you seeing visual feedback on the
multimeter display, you can listen, and when you hear the
beeping noise, then you have continuity from one side of
the circuit to the other.
The newest power supply testers are
really easy to use.
Most of them have this nice display on the front where I
can plug in the power directly from my power supply.
And then I can plug in other components into that same
power supply as well, and it will give me statistics about
voltages and information about what I happen to have plugged
in and how much voltage it happens to be using.
This is so easy to use, I don't have to stumble around
with probes on a multimeter on all of the different
connections.
I simply plug in all of my components, and this will tell
me everything.
If you're working at all with network connections, or serial
connections, or wide area network connections, then you
might also want to have some loopback plugs available.
These loopback plugs are used for testing physical ports,
and they're usually used in conjunction with a piece of
software that will send information out the port and
see if it is receiving information back in the
receive side.
You'll see these for serial ports, the RS-232, both the
nine and some of the older 25 pin connections.
For network connections, you'll see loopback plugs for
Ethernet or T1 or fiber type connections.
Keep in mind these are not cross-over cables like you
might see on the ethernet side of things.
These are very specifically-built loopback
cables the take everything coming out a transmit
connection and send them back through the receive connection
on that same device.
They look often like this-- very simple, you have traffic
coming in, you have traffic you're sending
right back out again.
And you usually don't need them unless there's a problem.
So it's useful to keep them somewhere close to the
hardware that you're going to be using them with.
You might want to have different loopback ports or
loopback cables for different types of media.
You may need some for fiber, you may need some for copper,
and you're going to need exactly the right interface
type for that loopback.
Just because it fits into an RJ-45 doesn't
mean it's for Ethernet.
It might be for a T1.
So make sure you know exactly what they're used for.
And if you'd like to make your own, you can
absolutely do that.
Here's a great website, spacehopper.org/5-in-1/ where
you can make an ethernet cable, a crossover cable, a
modem, a null modem, and a Cisco console cable, all from
one series of adapters.
If we're starting up our computer and we're getting
nothing from the start up, we may want to use one of these
power on self test cards that will look at the power and
give us some detailed error messages so that we can find
out a little bit more about what might be going wrong with
our hardware.