With small form-factor desktop PCs packing fewer PCI slots these days, a lot of folks are feeling an increasing need for PCI digitizer cards that can support many measurement channels.
There's also a large installed base of older CAMAC (computer aided measurement and control) multi-channel systems out there. Many users of these systems would like to upgrade to PC-based approaches that would permit the use of lower cost hardware and industry-standard post-acquisition analysis programs such as MATLAB.
One answer to the conundrum is a new board from from Strategic Test Corp. (Cambridge, Mass). Its UltraFast UF3132 is billed as the first digitizer PCIbus card to provide eight analog-input channels on a single card.
Significantly, Strategic's cards can be combined in multiple in an industrial-type PC to create systems with up to 128 synchronized channels.
A basic UF3132 has eight 12-bit A/D converters, providing a maximum sampling rate to 25-Msamples/s with true simultaneous sampling. Up to 256 MSamples of on-board memory can also record long signals at the maximum rates.
At its inputs, each channel has eight software-selectable input-voltage ranges spanning ±50-mV to ±10-V. you can also select of 50-Ohm or 1-MOhm input-impedances. These rnages and options let you optimize set-ups for each channel to closely match the characteristics of a sensor you may be digitizing. Here are the boards' software programmable parameters:
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A key point is that by using well-separated analog and digital circuitry, Strategic's dynamic specs are comparable with other digitizer cards having 14-bit A/D converters.
For example, UF3132 measured specifications include a signal-to-noise ratio (SNR) of better than 62-dB, with a THD (total harmonic distortion) spec of less than -62 dB. Spurious-free dynamic range (SFDR) is greater than 79 dB.
The UF3132 has two operating modes. In Standard Mode, input signals are digitized and then stored into onboard memory. At the end of the measurement you're able to put the data into your PC for analysis, or storage. This mode permits all eight channels to be used at the maximum sampling rates of up to 40 MHz.
An alternative FIFO Mode uses Bus Master capability of the card to continuously transfer data from the UF3132 to the PC during the measurement process. It lets signals longer than the available on-board memory to be generated.
Data is transferred continuously in a gap-free way across the 32-bit PCI bus at up to 50-Msamples/s. When using up to sixteen UF3122 cards as a synchronized system, Standard Mode lets the cards be used at maximum speeds without restriction.
The sampling rate of the signals can be programmed from 1-kHz to a 25-MHz maximum rate when using an onboard clock, or from DC to 25-MHz with an external clock signal. That's a feature often used to synchronize a card to external equipment.
In either case, you're free to specify any sample rate within these ranges. The software driver will automatically adjust the onboard clock signal hardware divider and PLL to suit. (As many digitizer cards limit the available sampling rate to a few pre-selected ranges, Strategic Test has an app note, entitled AN_01 Sampling Rate Determination, that describes this in greater detail. It can be downloaded from the company's Web site.
If you don't want to make your own programs, you can use Sbench measurement/oscilloscopes programs, running under Windows. These are supplied with the card. SBench supports all of the UF3132's features.
Using SBench, signals can be recorded and displayed graphically, then cursors can be used to make graphical analysis. Statistical calculations and FFTs (fast Fourier transforms) for spectral analysis, can be performed on the data.
More sophisticated analysis can be performed created using third-party programs, such as MATLAB. That done by exporting the signal data as ASCII/text files.
The UF3132 has an extensive list of available options, too. In addition to expanding the on-board memory from the standard 8 Msample capacity up to 256 Msamples (in various increments), there is a Multiple Recording option. It lets you record a series of waveforms at very high speed (over 20,000/s). Gated sampling starts and stops the recording when an external TTL signal changes level.
You can also set up star hub synchronization for synchronizing the clocks and triggers of up to 16 cards. There's also a Digital Inputs option that adds 32 digital inputs; these record at the same speed as the A/Ds.
An Extra I/O option can also be chosen for controlling external equipment or reading external status information, with the additional 24 slow digital I/O channels and four analog 12-bit D/A output channels.
Okay, how much will these cards set you back? Well, an UltraFast UF3132 with 8-Msample memory costs about $12,200. A 16 Msamples version is about $13,100.
A 32 Msamples spin will cost about $14,300. 64 Msamples cost $15,450. A 128 Msamples card is a bit under $17,000. A maximum 256 Msamples version is priced at about $19,600. Of course, OEM discounts can be negotiated.
Free software drivers for Windows XP, Windows 2000, Windows NT, Windows ME, Windows 98 and Linux are supplied, while drivers for MATLAB, LabVIEW, Agilent's VEE and DASYLab are available as options.
The SBench measurement and signal generation programs are also freebies. Source code programming examples in VisualBASIC, C, C++, and Delphi are also supplied fre of cost.
The boards also come with a two year hardware warranty and lifetime software updates---including future Windows and Linux drivers. Technical support is provided at no cost for the product's lifetime.
For more details, contact company president Bob Giblett at Strategic Test Corp., One Broadway, Suite 600, Cambridge, Mass. 02142. Phone: (617) 621-4010. Fax: (617) 577-1209. E-mail: email@example.com