Page 1234 - The Mechatronics Handbook

Hardware Options

Many different hardware platforms are available for data-logging systems. The platform choice depends
on your requirements for size, operating environment, and installation. Although the combinations are
nearly endless, platforms for PC-based data-logging can be broadly broken down into four categories:
portable, desktop, rack mount/industrial, and distributed. One of the key benefits of PC-based data-
logging systems is that the same data-logging software scales across all of these platforms.
Portable data-logging solutions are needed in a variety of applications, such as in-vehicle data logging
or field-testing of equipment. Portable PC-based solutions use laptops for the computer, and measure-
ment hardware that is designed to be easily portable. Figure 50.9 shows a portable, PC-based data-logging
system from National Instruments. The digitizer is a plug-in PCMCIA data acquisition card, which cables
to small, laptop-sized boxes for signal conditioning and connectivity. Portable systems are typically limited
to less than 40 channels due to size constraints.
Desktop systems, like the one shown previously in Fig. 50.3, use measurement hardware designed to
work with standard desktop PCs. Desktop systems are ideal for a wide range of laboratory-based data-
logging applications, such as validation testing of new product designs. Since fixed desktop systems are
not as constrained by size, the signal connectivity and conditioning functions are typically accomplished
by a modular front-end signal conditioning system that provides the capability to measure a wide range
of sensor and signal types and to easily expand to log hundreds of channels.
Many times desktop systems take up too much space or do not fit well in environments like large lab-
oratories or manufacturing facilities. In these cases, the more compact and clean solution of a modular
industrial PC, based on the PXI or CompactPCI standard, might be a more appropriate data-logging
solution. Figure 50.10 is an example of a PXI-based data-logging system. One modular system contains the
PC, DAQ board, signal conditioning, and connectivity. These systems are designed to be rack-mountable,
so they can be cleanly installed into an industrial or laboratory environment.
Finally, some data-logging systems need to be distributed away from the PC. This is the case when
you need to log data from multiple locations around a facility, such as when logging the performance
parameters of a chemical plant. Distributed logging systems should be compact so they can be mounted

FIGURE 50.9 Portable PC-based data-logging system.

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