Board Versus Box: The Age-Old DAQ Dilemma

Since the beginning of PC-based data acquisition and control in the 1980s, one question has remained a constant consideration for all who would specify a new DAQ system. Is this application better served by an external I/O “box” connected to the PC via some communications link, or an internal “board” system plugged into a slot within the computer? If anything, this question has become more complicated as technology has progressed.

Today, you have a wider — and better — choice of interfaces for your DAQ system than ever before. External box systems based on 100Base-T and Gigabit Ethernet (including LXI), USB, GPIB, CAN, RS-232/485, as well as a variety of proprietary interfaces, are available. On the plug-in board side of the coil are interfaces for PCI, PXI, PCI Express, Cardbus and ExpressCard. Even boards for the original IBM PC’s ISA bus are still available. To further complicate matters, hybrid systems like UEI’s popular RACKTangle series offer the advantages of an external box with the flexibility and reconfigurability of a board system.

Choosing what’s best for a given application is not an easy task. Some of the parameters used to compare interfaces are:

• system accuracy,
• I/O count,
• distance between DAQ system and sensors,
• system portability,
• expandability,
• flexibility,
• overall cost,
• bandwidth (DAQ speed),
• expected product life.