Electronic Design

Digitizer Maximizes Test Data Throughput With Low Power Consumption

The first step in most test and measurement applications today is to acquire and digitize the test signal for further storage and analysis with software on a PC. A good digital oscilloscope is one common way of doing this. But for some tests, an oscilloscope is overkill and too expensive. For many laboratory, production, and field testing applications, a smaller digitizer is ideal. Agilent Technologies' DP1400 digitizer is one option for such situations.

Late last year, Agilent acquired Geneva, Switzerland-based Acqiris, a privately held company that makes leading-edge digitizers and analyzers for the commercial, industrial, and government markets. The DP1400 is Agilent's first Acqiris product, which was designed to provide superior measurement fidelity with minimum power consumption, reduced size, and maximum data throughput.

The DP1400 is a dual-channel digitizer with 8-bit analog-to-digital converters (ADCs) each sampling at 1 Gsample/s (Fig. 1). It plugs into a standard 32bit/66 MHz PCI bus in a PC, and it's small enough to be used with even the most compact PCs. And by combining commercial off-the-shelf (COTS) ICs and the company's own unique ASIC, Acqiris has produced a digitizer with the lowest power-consumption ratings ever.

Total power usage is less than 15 W with full-bore sampling on both channels. This makes the digitizer a good choice for field applications and where battery power may be needed. Typical applications include medical imaging (ultrasound), hard-disk-drive testing, semiconductor test, mass spectrometry, scanned infrared absorption techniques, and radar.

One of the key specifications of the DP1400 is a full dc to 1-GHz analog bandwidth on each channel. The digitizer is set up so you can alternate or interleave the ADCs on a single channel to achieve a full 2-Gsample/s sample rate if needed. The inputs are 50-Ω ac or dc coupled. Input voltage ranges from 50mV to 5 V full scale. A total of 256 kbytes of fast RAM supplies buffer storage (128 kbytes per channel).

The DP1400 includes a low-phase-noise internal clock source, but an external clock may be used. An external trigger input is also provided. When more than two channels of data acquisition are required, multiple DP1400s may be synchronized to one another using the 2-GHz auto-synchronization bus (AS_Bus_2) designed for triggering and clock distribution to several digitizers.

Data storage and buffering represent major problems for users of fast digitizers. The host PC memory and hard drive are typically used, but sometimes, even RAID storage is needed. The DP1400 helps such situations with its unique onboard buffer memory.

Available as an option, the Simultaneous Multi-buffer Acquisition and Readout (SAR) provides for segmenting the 256kbyte RAM into three buffers. As data is acquired into one buffer, another can be read out through the PCI bus. With the 32-bit/66-MHz PCI bus, this means four byte samples can be transferred at a 256-Mbyte/s rate (Fig. 2).

In applications where the total data rate of the acquisition is below the PCI data bandwidth, the DP1400 with SAR mode can acquire continuously without missing any events. Inter-segment dead time between buffer memory segments is less than 350 ns.

Device drivers for Windows, VxWorks, LabViewRT, and Linux are provided. Application code examples for Matlab, C/C++, Visual Basic, LabVIEW, and LabWindows/CVI are included. Prices for the DL1400 start at $9490. Delivery is eight weeks from receipt of order.

Agilent Technologies Inc.

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