Sample Transport and Storage - Field Sampling: Principles and Practices in Environmental Analysis - page 214

uninterruptible power supply (UPS) is a good way to help prevent data loss. These power
supplies will keep the computer running for a short period of time, which is usually long
enough to allow data to be saved, and the computer can be turned off when there is a
power failure. A safer strategy, however, is to constantly and conscientiously back up
data. Keep in mind that a UPS unit does not preclude the need for daily backup; it can fail
and it cannot prevent failure of other components of a computer.
There are five major ways to store data; 3.5 floppy disk, zip drives, hard drives, CDs,
and DVDs. A 3.5 floppy disk can be used and has the advantage that it can easily be
carried from place to place and can be kept with the COC. These disks, however, are
limited in the amount of data they can store. A hard drive is a convenient storage device
and can typically hold large amounts of date. Hard drives are usually internal to the
computer, however, so either data are transferred to the hard drive when the office
receives then or the computer must go with the sample. This obviously will not work with
a desktop computer containing a hard drive, but is feasible with a laptop. There are
external hard drives accessible through a computer's USB port. This hard drive can be
carried from computer to computer, but transport is not easy because of its nature and its
susceptibility to damage and data loss.
Either internal or external zip drives are also available. These drives and their
removable disks hold a moderately large amount of data, and the disk can easily be
transported or kept with the COC. External zip drives are small enough to carry around
conveniently, and if they connect via a USB connector, can be connected to available
computers at any location. One important drawback to all the storage devices discussed
so far is that the data on them can be lost or erased.
For a permanent record, a CD or DVD recording can be made of the COC and the
accompanying information (usually referred to as burning). For a permanent record a
CD-R or DVD-R, (“read only”) must be used. There are CDs that can be rewritten, but
for COCs these are not recommended. Once a CD-R is burned, it is a permanent record of
the COC and accompanying explanations. A CD player/burner or DVD player can be
bought as an internal or external unit. An external unit would then be available to carry
between computers. DVDs hold a great deal more information than CDs, so a single
DVD may be all that is necessary to store all the information gathered about a particular
field, including maps and pictures.
Newer types of storage devices, flash memory, memory sticks, and flash cards, are also
available. These are used extensively on digital cameras, can also store data and are
relatively small. They hold about the same amount of data as a zip disk; that is, up to 256
megabites (MB) in a very small unit. They are particularly useful if a number of pictures
are to accompany the sampling plan, and can easily be carried from place to place and
used on any number of computers, both desk and laptop. A drawback is that some of
these devices require a special reader or port to transfer data from these devices to a
computer. Two other potential drawbacks are that some seem to use significant amounts
of energy, and this may be a problem when they are used with digital cameras, which
have dry cell batteries. The second drawback is that they can be erased, and so data can
accidentally be lost. A number of common computer storage devices are shown in Figure
8.4. Table 8.3 lists various storage devices and gives some information about their
characteristics.