ADC modules target chromatography, handle other applications

-- EDN, 12/7/2000

Data Translation designed the DT9821 and DT9822 USB data-acquisition modules to meet the needs of chemical-analysis systems—liquid and, to a smaller extent, gas chromatographs (Picture).

But you can use the units in many other applications that demand high resolution (to 24 bits—22 bits noise-free—at 7.5 samples/sec/channel) at conversion speeds to 960 samples/sec/channel (with 16.5 bits of noise-free resolution). Both units provide four high-sensitivity, variable-resolution analog inputs, each of which provides a gain that you can separately program in seven binary steps. The most sensitive range is ±0.039062V full-scale.

You can safely float the four input channels' common ground reference at ±500V with respect to the chassis, and you can operate each channel with a different common-mode voltage in the range of ±5V with respect to the floating ground. You can also separately start (trigger) and stop each of the four delta-sigma ADCs. The hot-pluggable modules receive all of their operating power from the USB dc-power bus. Each module provides a pair of internal clock oscillators. One optimizes rejection of normal-mode harmonics of a 60-Hz ac line; the other does the same thing for harmonics of 50 Hz.

Both of the 100×160×

50-mm modules provide eight digital inputs and eight digital outputs. The DT9822 also provides a pair of 16-bit-resolution, ±5-mA analog outputs that swing to ±5V and drive 1 nF without oscillation. Except for the USB connection, all I/O connections are on a single 37-pin D-subminiature connector. Data Translation offers screw-terminal adapters that mate with this connector. The DT9821 costs $1895; the DT9822 costs $1995. The prices include several menu-driven, ready-to-run software applications; a system-development-software kit; and 32-bit device drivers for Windows 98, Windows 2000, and Windows ME.

Data Translation Inc, 1-508-481-3700, www.datatranslation.com.

—by Dan Strassberg