Industrial
Engineering Assignment
Design
of Magnetic Tape
Presented by
Sakshi Gupta(Roll
No. -85)
Reeti Pal (Roll
No.-106)
LEARNING
OBJECTIVES
Describe the physical properties of magnetic tape in terms of:
·
The Three Basic Materials Used To Make magnetic Tape
·
The function of the magnetic tape's base material, oxide
coating, and binder glue
·
Describe the two types of magnetic recording tape
·
Describe the following types of tape errors and their effects on
magnetic tape recording: signal dropout, noise, skew, and level
·
Describe the following causes of magnetic tape failure: normal wear,
accidental damage, environmental damage, and winding errors
·
Describe the purpose and makeup of tape reels and tape cartridges
·
Describe the two methods for erasing magnetic tape, the characteristics
of automatic and manual tape degaussers, and the procedures for degaussing
magnetic tape
·
Describe the proper procedures for handling, storing, and packaging
magnetic tape, tape reels, and tape cartridges
PHYSICAL PROPERTIES OF
MAGNETIC TAPE
The three basic materials used to make magnetic tape are (1) the base
material, (2) the coating of magnetic oxide particles, and (3) the glue to bind
the oxide particles onto the base material. See figure 2-1.
Figure 2-1. - Magnetic tape construction.
BASE MATERIAL
The base material for magnetic tape is made of either plastic or metal.
Plastic tape is used more than metal tape because it's very flexible, it
resists mildew and fungus, and it's very stable at high temperatures and
humidity.
OXIDE COATING
Oxide particles that can be magnetized are coated onto the base
material. The most common magnetic particles used are either gamma ferric oxide
or chromium dioxide. It's very important that these magnetic particles are
uniform in size. If they're not, the tape's surface will be abrasive and will
reduce the life of the recorder's magnetic heads.
An ideal magnetic particle is needle-shaped. It's actual size depends on
the frequency of the signal to be recorded. Generally, long particles are used
to record long wavelength signals (low-frequency signals), and short particles
are used to record short wavelength signals (high-frequency signals).
GLUE
The glue used to bond the oxide particles to the base material is
usually an organic resin. It must be strong enough to hold the oxide particles
to the base material, yet be flexible enough not to peel or crack.
TYPES OF MAGNETIC
RECORDING TAPE
There are two basic types of magnetic recording tape in common use: analog and digital.Analog magnetic tape is used to
record, store, and reproduce audio and instrumentation type signals. These
signals are usually in a frequency band from very-low frequency (VLF) to 2.5
MHz. Digital magnetic
tape is used to record, store, and reproduce computer programs and data. It's
base material thickness is about 50 percent thicker than analog magnetic tape.
This allows the digital tape to withstand the more strenuous starts and stops
associated with digital magnetic recorder search, read, and write functions.
Digital magnetic tape is also held to much stricter quality control
standards.
It's important not to have any blemishes or coating
flaws on the tape's surface. Because, if you lost one digital data bit, your
computer program or data would be bad. In contrast, losing one microsecond of
an analog signal is not nearly as critical.
TAPE ERRORS AND THEIR
EFFECTS
Four types of tape errors that will degrade the performance of a
magnetic recording system are signal
dropout, noise, skew, and level (signal amplitude changes).
DROPOUT ERRORS
Signal dropout is the most common and the most serious type of tape
error. It's a temporary, sharp drop (50% or more) in signal strength caused by
either contaminates on the magnetic tape or by missing oxide coating on part of
the tape.
During recording and playback, the oxide particles on the tape can flake
off and stick to the recorder's guides, rollers, and heads. After collecting
for awhile, the oxide deposits (now oxide lumps) break loose and stick to the
magnetic tape. As the tape with the lumps passes over the head, the lumps get
between the tape and the head and lift the tape away from the head. This causes
the signal dropouts. Although oxide lumps cause most signal dropouts, remember
that any contaminate (such as dust, lint or oil) that gets
between the tape and the head can cause signal dropouts.
NOISE ERRORS
Noise errors are unwanted signals that appear when no signal should
appear. They're usually caused by a cut or a scratch on the magnetic tape. It's
the lack of oxide particles at the cut or the scratch that causes the noise
error.
SKEW ERRORS
Skew errors only occur on multi-track magnetic tape recorders. The term
skew describes the time differences that occur between individual tracks of a
single magnetic head when the multi-track tape isn't properly aligned with the
magnetic head.
There are two types of skew errors: fixed and dynamic.
Fixed skew happens when properly aligned magnetic tape passes an improperly
aligned magnetic head. Dynamic skew happens when misaligned tape passes a
properly aligned head. This type of skew is usually caused by one or more of
the following:
A misaligned or worn-out tape transport system.
A stretched or warped magnetic tape.
A magnetic tape that is improperly wound on a reel.
LEVEL ERRORS
Magnetic tape is manufactured to have a specified output signal level
(plus or minus some degree of error). Level errors happen when the actual
output signal level either drops or rises to a level outside the expected
range. For example, if a magnetic tape is rated for 10 volts ( +/-10%), any
output signal level below 9 volts or above 11 volts is a level error. Level
errors are caused by an uneven oxide coating on the magnetic tape. This can
come from either the original manufacturing process or from normal wear and
tear.
Some causes of level errors are permanent and cannot be removed by any
means. For example, a crease in the
tape, a hole in the oxide, or a damaged edge. Other causes of level errors are
removable and may be cleaned off the tape. For example, oxide flakes or clumps,
metallic particles, or dirt are removable.
References:
Wikipedia
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