Excerpt from
"Portable Data Collection Solutions. Finding One
That's Right for You." by Dirk Disharme.
Portable Data Collection
Solutions.
Finding One That's Right
for You.
by Dirk Dusharme (columnist
for Quality Digest Magazine)
All best-of-industry quality processes
depend upon data collection. For manufacturing processes,
the data often come from measurement instruments used
to collect spatial, environmental, electrical, mechanical
or physical characteristics from the part being manufactured.
Twenty-five years ago, most measurement data were
collected manually. But as computers became smaller,
more affordable and faster, this function was turned
over to them, decreasing the time and increasing the
accuracy of data collection.
Years ago, setting up an automated
shop floor data collection system involved straightforward
decision making: You either bought a dedicated data
collection system, had one custom-designed for you,
or you put one together yourself using a PC, a data
collection box, a multiplexor and some sort of data
collection software to communicate with the whole
mess.
But these dedicated systems were
large, usually sitting either on a benchtop next to
where measurements needed to be taken, or on roll-around
carts for limited portability. Unless you were built
like Arnold Schwarzenegger, you probably didn't lug
these systems onto an aircraft wing to take measurements.
For data collection from a remote location, you did
it the old-fashioned way: a caliper in one hand, a
clipboard in the other and a pencil clenched between
your teeth. It was tiring, time-consuming and error-prone.
Worse yet, the handwritten data had to be transcribed
back into a computer for analysis, requiring more
time and providing more opportunities for error.
Fortunately, those days are long
gone. Portable data collection units are now available
in a range of different sizes. Each will upload a
measurement process (often called a "route")
from a host computer and, once on the shop floor,
guide the operator through the measurement protocol
using onscreen prompts, greatly reducing training
time. They all have an LCD screen to display measurement
instructions and results, including alarms for out-of-control
processes and ports that will connect to almost any
measurement device. All allow alphanumeric entry either
through a QWERTY keyboard or a small alphanumeric
keypad. All provide varying degrees of on-the-spot
SPC data analysis and will download data to a PC workstation
for further data analysis. The main differences between
products is the number and types of devices they can
connect to, the size of the screen and keyboard, the
amount of on-the-spot data analysis, battery life,
ease of use and special functions.
Is a portable for you?
Although all that functionality in
a small package might sound too good to pass up, a
portable data collector isn't for everybody. "You
go to a portable data collector because you have to,"
says Erich Shroeder, product manager for DataMyte,
an industry leader in portable data collection systems.
"If your parts are spread out or too big, you
go to a portable."
It also depends upon the job function
of the person doing the work, adds Frank Skog, DataMyte's
application manager. "For the person whose only
job is to collect data, a portable makes sense,"
he explains. "For a person who takes data while
working at a milling machine for instance, a dedicated
system may make more sense."
As supplier audits become more the
norm and, in some cases, mandated, the ability to
quickly set up and take measurements at a supplier's
location may also dictate the use of a portable. Most
portable data collectors give instant reporting, letting
auditors make crucial decisions within minutes instead
of hours or days.
A portable probably isn't for you
if you need to monitor a large number of devices.
"Someone once called me up asking to collect
32 channels of analog data," recalls Oliver King-Smith,
president of Tescina Inc., the leader in Palm OS-based
data collection. "It quickly became apparent
that by the time I was done, he would have a small
suitcase filled with connectors that he would then
plug into his hand-held. If the amount of wires and
connectors is vastly greater than the size of the
hand-held, you need to start asking yourself if using
a PC might not make more sense."
Finally, if you don't need the functionality
of a desktop system, a portable may be more cost effective--even
when used as a dedicated data collector.
What to consider
So what things should you think about
before deciding on a portable data collector?
Location. Depending on where you
need to take measurements, size and weight are considerations.
Will the unit and any adapters physically fit where
they need to go? Will the operator have to carry the
collector continuously or can it be set down? A four-pound
unit slung over your shoulder will feel like 40 pounds
after eight hours.
One-, two- or no-handed operation:
Lacking a flat surface, will the operator need to
hold the unit in one hand and measure or input data
with the other, or will the operator need both hands
free? This ties into the size and ergonomics of the
unit as well as its user interface. Some come with
a footswitch for triggering actions on the unit, leaving
both hands free.
Battery life. All portables run on
battery power; some can also run on line power. If
the unit you are considering uses only battery (or
line power isn't available at the site), will the
battery last long enough for your application?
Text entry. Does your application
require the operator to input a lot of free-form text?
If so, a telephone-style keypad or pen stylus will
be tedious. Consider a portable with a QWERTY keyboard.
Ruggedness. What kind of environment
will the unit operate in? Is there a lot of dust,
spray or other contaminants? Verify with the manufacturer
that the unit is designed for use in such environments.
Display. Most portables have a small
LCD display. You need to determine how the display
will be used in your application and whether a small
display will tire the operator. If you constantly
need to refer to run charts or other data, a larger
screen may be called for.
Desktop analysis. Although all the
units shown here will export collected data for use
in any third-party analysis software, each is designed
to connect directly with one or more popular SPC software
packages. If your company is tied into specific analysis
software, consider a portable that works directly
with your package.
Cabling. Some portables require special
adapter cables for each type of gage to be used; others
work directly with the cables supplied by the gage
manufacturer. If you already have a lot of manufacturer-supplied
cables, this may be a consideration.
Wireless. Do you want or require
wireless communication with your portable? One advantage
with a wireless system is data integrity; the data
is sent to a host computer instead of being stored
on the unit. If the unit is broken or lost, you still
have the data. A wireless system also allows functions
such as e-mail and access to documents stored on the
host computer. How-ever, wireless units may not work
well in areas with a lot of electrical noise (e.g.,
motors or welders), which can cause dropouts (think
cell phone). Before buying a wireless system, make
sure that it will work in your environment and that
the unit has some sort of data integrity system that
prevents lost data in the case of dropouts.
Ports. How many gages and gage types
do you need to monitor at one time?
Memory. How much data will you collect
before downloading the unit? This isn't as much of
an issue with wireless units.
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