Information Technology Reference
In-Depth Information
troubleshooting equipment and diagnostic/measurement equipment. Basic trouble-
shooting equipment consists of devices that check continuity, DC resistance, and simple
wire maps. Diagnostic/measurement equipment is used to measure cable parameters,
determine compliance with standards, and diagnose specific cable problems.
Which type of test equipment should you have? The answer to that question
depends on the type of work you need to do. If you do any amount of cable instal-
lation or troubleshooting, you need most of the basic test equipment items described
below. If you need to test or certify cable to cabling standards, you will need a field
tester capable of meeting the accuracy requirements of the category you are testing.
Fiber optic cable requires special test equipment, even for routine tests. For a fiber-
optic installation, you should have fiber attenuation measurement equipment, at the
least, and you may need more sophisticated scanning equipment to locate fiber faults.
How much money should you spend for test equipment if you are the network
manager? A good rule of thumb is to expect to spend 2% to 5% of the value of your
networking equipment (including workstations and file servers) for test, analysis,
and monitoring equipment. As an alternative, you could allow 10% of the value of
just the cable, hubs, and bridges for test equipment. The point is that you need to
have a reasonable capability to test and troubleshoot your network. Without the
proper equipment, you are flying blind. You will suffer from periodic cases of equip-
mentus substitutis (as evidenced by lots of running around while carrying comput-
ers, hubs, and cables). To avoid this syndrome, simply obtain the necessary test
equipment to simplify and speed your troubleshooting. You also need a certain
amount of test and monitoring equipment to verify the health of your network and
to spot trends that may have a negative effect on performance in the future.
The rest of this chapter is devoted to the essential test equipment you will need
and the methods to use in employing the more sophisticated testers. In addition to
the Physical layer equipment we show here, you may also have need for LAN proto-
col analyzers that deal with the higher layers of networking. These protocol tools will
help you answer the age-old question, “OK, if it's not the cable, then what is it?”
Continuity Testers (Voltmeter, Continuity Tester)
The most basic item of test equipment that should be in your toolbox is a good elec-
tronic voltmeter. This voltmeter should be able to read DC volts, AC volts, and
ohms. It should be durable and have an easy-to-read display. A “hold” function is
also nice, as it allows you to make a measurement and later read the display. This
is great for those times when you are deep inside a punchdown block or in an area
with low light. Many voltmeters also have a continuity function with an audible
beep (some of us consider this a mandatory requirement).
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