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PCI signal generator plug-ins make performance tradeoffs

Posted: 22 Sep 2005 ?? ?Print Version ?Bookmark and Share

Keywords:pci bus? gagescope? oscilloscope? sdk? software development kit?

One of Gage's latest products

In the mature world of PC instrumentation, Gage Applied Technologies continues to innovate and expand its already extensive line of PCI bus multi-MHz to GHz digitizers and scope cards, analog signal generator cards, and digital I/O cards. These wares are supported by the company's programming-free GageScope oscilloscope software and an array of SDKs (software development kits).

The GageScope oscilloscope software runs under Windows 98, Windows ME, Windows NT, Windows 2000 and Windows XP. It lets you capture and display signals on your PC, giving you features such as FFTs (fast Fourier transform) analyses, waveform parameter analysis, extended math, and averaging. The software also supports downstream analysis packages such as MATLAB, LabVIEW, and Mathcad.

The DAC cards
These three new PCI plug-ins from Gage give you a number of tradeoffs in speed and channel capacity. As such, they should prove cost effective in a variety of applications, depending on how many signal lines you need to generate, and what data rates you want to generate them at. The tradeoff in the equation is memory capacity per channel.

The speed demon of the new line-up is the CompuGen 11G. As noted in the press release, its architecture supports a D/A conversion rate of a billion samples/s with 12-bit vertical resolution that gives you 4096 levels.

In use, the 11G lets you generate a near limitless number of aperidodic analog, as well as digital signals. In use, these waveforms are generated using a digital representation of the desired waveform that's stored in a 4-Msample on-board memory. The stored pattern is then converted into an analog signal using the system's high speed DAC (digital-to-analog converter).

Note that the 11G can also be operated in the same PC as one of Gage's CompuScope digitizer cards. You could, therefore, set up a plug-in-based stimulus/response system using multiple cards.

Two run modes
Let's look at the 11G's operating modes. It has both a Free Run mode and a triggered mode. Free Run supports continuous repetitive signal generation; on-board memory is seamlessly and endlessly looped during signal generation. Patterns advance from the last sample back to the first in one clock cycle.

In triggered mode, the 11G generates pre-programmed waveforms in a single-shot fashion every time a trigger occurs. The trigger can be a software trigger or an external signal. Using external triggering, the CompuGen 11G can generate a single-shot waveform at the rising edge of a TTL pulse at the external trigger input. Using software triggering, the generation of a single-shot waveform occurs when a software command is issued.

In either case, the trigger is automatically re-armed in hardware after single-shot waveform generation to await another trigger event. There's no software interaction so re-arming occurs very quickly. Also, by issuing multiple triggers, you can create waveform bursts. The 11G delivers a 0.5V (p-p) signal with rise- and fall-times of 300ps.

Four channels
Let's now look at the middle-of-the-line CompuGen 4300 plug-in. Like the 11G, it can be used to generate analog and digital signals, but 4300 gives you four channels of simultaneous data generation. The 4300 is also equipped with a 4-Msample memory array, but unlike the 11G it's shared equally among the card's four channels, with 1-Meg per channel available.

The CompuGen 4300 plug-in generates analog outputs at a maximum D/A conversion rate of 300MS/s. Like the 11G, it also dishes up 12-bit vertical resolution, and lets you choose free running or triggered modes of signal generation. It's four DAC outputs deliver signals over a 2-V (p-p) range, with single-ended outputs at 50? ports. There's an on-board programmable attenuator that provides up to 30dB of attenuation in 0.5dB increments.

Eight channels
Finally we come to the new CompuGen 8150. It can generate signals at a maximum conversion rate of 150MS/s. Like its higher speed counterparts, it too delivers 12bit vertical resolution. However, the 8150 can dish up eight channels of simultaneous signals. Like the 11G and the 4300, the CompuGen 8150 is equipped with four megs of memory, and it's shared equally among the card's eight channels. That gives you 512-k per channel.

Like the 4300, the 8150's multiple DAC outputs deliver signals over a 2V (p-p) range, with single-ended outputs at 50? ports, and with programmable attenuation.

As in times past, Gage is reluctant to respond to my request for pricing specifications. The company, it seems, would rather have you log onto its website so it can qualify you as a potential customer. This is unfortunate, as pricing is indeed a spec, and even a ballpark figure gives you a basic idea about whether the product is for you or not.

- Alex Mendelsohn

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