eFunda: Introduction to Data Acquisition Technology
engineering fundamentals Data Acquisition Introduction
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Data Acquisition (DAQ) technology provides the link between the data-generating sensors and data-storing recording devices. DAQ can also provide the means for driving external actuators from a computer, by the generation of external excitation signals. DAQ technology includes both hardware and software.

Thanks to the recent advancements in processor technology, the low cost personal computer is now the most important carrier for data acquisition cards. The high clock speeds of modern central processing units (CPUs), such as Pentium and PowerPC, enables higher sampling rates. This along with high performance bus architectures such as PCI, cheap RAM, and fast voluminous hard disks make long-term continuous measurements possible.

Traditionally, the clock speed of the computer CPU can significantly affect the performance of the DAQ system. However, newer direct memory access (DMA) transfer technology speeds up the system by using dedicated hardware to transfer data directly into system memory. Thus, the CPU is not burdened with moving data and is therefore free to engage in more complex processing tasks. In addition, if an application requires real-time processing of high-frequency signals, a dedicated digital signal processing (DSP) chip can be built-in on the DAQ board to share the work load of the main processor.

Another important development is portable data acquisition based on laptop computers with PCMCIA cards. This configuration allows more convenient field measurements that used to be troublesome for practicing engineers.

Emerging broadband internet and broadband cellular phones outperform traditional modem hookups using RS-232 or RS-485 serial communication ports. These emerging communication technologies will make remote monitoring and access measurements more achievable.

In short, the current level of data acquisition technology, although still not perfect, is far more effective and efficient than a decade ago. In the future, one can expect even more affordable and accurate measurement instruments, some that could be fitted into computers as small as modern hand-held calculators or personal digital assistants.

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