Data Acquisition (DAQ) Introduction

continued from the main introduction

Powerful DAP boards excel at applications that require extensive real-time computation: FFTs that keep up with the acquisition rate, for instance. A top-of-the-line DAP can perform a 16k-point FFT at a sustained rate of 1.4M samples per second. Imagine what it does to FIR filters.⁴

Typical real-time procedures that any DAP can perform include continuously sampling high-speed data while watching for a trigger event, and then passing pre-trigger and post-trigger blocks of data to a Windows or Linux application. A trigger event in a signal can take many forms: a level, a slope, a minimum within a time period, a maximum, and so on. More complex actions potentially triggered by an event include other real-time processes performed by DAPL on the DAP board and direct control of analog or digital outputs.

The benefits of onboard intelligence in the PC environment depend on the particular application. They cover a spectrum ranging from helpful through essential. You can look at some sample applications to develop a sense of how much onboard intelligence matters to some of our customers.⁵

Onboard intelligence allows synchronization between several DAPS in a single PC – without PC interrupts. For networked PCs, onboard intelligence allows synchronization between hardware in different DAPcell⁶ software servers over a parallel DAP-to-DAP network independent of PC-network delays. Microstar Laboratories has shipped such systems with many hundreds of channels. A scalable benchmark server shows that such a distributed system could acquire data at over 50 million samples per second.⁷

Footnote 4 [FIR filters]: Technical Note TN-164 gives the details.
Footnote 5 [applications [...] customers]: See sample applications on our Web site.
Footnote 6 [DAPcell]: The DAPtools Standard package and the DAPtools Professional package, described on pages 6 and 7 of the catalog, include, respectively, DAPcell Local Server software and DAPcell Network Server software.
Footnote 7 [50M samples per second]: A single DAPcell server PC can support up to 7 DAP boards as standard. In the benchmark server, Microstar Laboratories used 4 DAP boards, each with an overall data acquisition rate of 1228.8k samples per second, and logged to disk at the full acquisition rate: 4.9152M samples per second. A single DAPcell client PC, requesting the disk logging service from 11 servers configured like the benchmark server, then can log to disk at an overall rate of 54.0672M samples per second.

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Data Acquisition (DAQ) from Microstar Laboratories