Page 1224 - The Mechatronics Handbook

FIGURE 50.1 PC-based data-logging application—performance testing of refrigerator designs.

50.2 Historical Background

The earliest form of data logging involved taking manual measurements from analog instruments like
thermometers and manometers. These measurements were recorded into a written log, along with the
time of observation. To view trends over time, people manually plotted their measurements on paper.
In the late nineteenth century, it became possible to begin automating this process with machines, and
strip chart recorders evolved. Strip chart recorders are analog instruments that translate electrical impulses
from sensors into mechanical movement of an arm. A pen is attached to the arm, and long rolls of paper
are moved at a constant rate under the pen. The result is a paper chart displaying the parameters measured
over the course of time. Strip chart recorders were a great leap over manual data logging, but still had
drawbacks. For example, translating the traces on the paper into meaningful engineering measurements
was tedious at best, and the data that was recorded took up reams and reams of paper.
With the development of the personal computer in the ’70s and ’80s, people began to leverage computers
for analysis of data, data storage, and report generation. The need to bring data into the PC brought about
a new type of equipment for data logging, the dataloggers. Dataloggers are stand-alone box instruments
that measure signals, convert to digital data, and store the data internally. This data must be transferred
to the PC for analysis, permanent storage, and report generation. Data is typically transferred either by
manually moving a storage device, like a floppy, from the datalogger to the computer, or by connecting
the datalogger to the PC through some communications link, like serial or Ethernet.
In the 1990s, a further evolution in data logging took place, as people begin to create PC-based data-
logging systems. These systems combine the acquisition and storage capabilities of stand-alone data-
loggers with the archiving, analysis, reporting, and display capabilities of modern PCs. PC-based logging
systems finally enabled full automation of the data logging process. The move to PC-based data-logging
systems was enabled by the following three technological enhancements:
1. Increasing reliability of PCs
2. Steadily decreasing cost of hard drive space on PCs

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