16-Channel Instrumentation Amplifier Card With Programmable Gain and AC/DC Coupling
The PGA-16 is a 16-channel instrumentation amplifier with differential input, single-ended output, programmable AC or DC input coupling and pre-filter gain. The PGA-16 may be used as an input conditioner for any A/D converter or for our AAF-16 anti-alias filter card.
Each channel of the PGA-16 has its own instrumentation amplifier with differential inputs. Using the included software, you can configure each channel independently for a gain of 0.5, 1, 2, 5, 10, 20, 50, 100, 200, 500, or 1000.
Performance on the PGA-16 is outstanding from DC to 200kHz, and a slew rate of 9V/microsec allows the card to handle large, fast signals.
Advantages of Pre-Filter Gain
Many data acquisition boards provide multiple input ranges by using software-programmable gain amplifiers. While this kind of gain lets you change the input range, it also can present a new problem: amplification of electrical noise added by the measurement system to the signal.
If the gain is on the A/D board (post-filter gain), it amplifies not only the signal, but also any noise added by common measurement-system sources, such as the signal conditioner, the computer interconnections, or the A/D input circuit. On the other hand, if the gain is directly on the signal (pre-filter gain), only the signal is amplified. Pre-filter gain, which the PGA-16 provides, can make the low-level signal override the measurement-system noise, providing a dramatic improvement in signal-to-noise ratio. Post-filter gain cannot, since it amplifies the measurement-system noise along with the signal.
In addition, the A/D board post-filter gain usually multiplexes multiple channels into a single amplifier. The settling time of the amplifier can cause artificial signal errors unless delays are built into the sampling control. With the PGA-16, each channel has its own full-time amplifier, eliminating this restriction.
Alligator Technologies has developed both menu-driven and driver-level software for controlling key functions on the PGA-16.
Menu-Driven Software - The menu-driven program uses a single setup screen with pop-up menus for selecting such key parameters as gain setting, AC or DC coupling and board address. Once selected, a combination of settings can be saved as a PGA-16 description file. Once saved, the settings stored in this file can be easily applied to other boards by selecting the file.
DOS and Windows Drivers - If you prefer to develop your own programs, the PGA-16 comes with DOS and Windows linkable libraries that provide high-level functions for configuring and controlling the PGA-16. Example application programs are provided for popular compilers, including Visual C++, Visual Basic, and Pascal.
LabVIEW Driver - PGA16.LLB VI can be graphically assembled with other VIs in a LabVIEW block diagram to create a complete instrumentation system.
HP VEE User-Object - Both 16- and 32-bit user-objects for HP VEE.
Connection to Your Data Acquisition System
Inputs from the signal sources connect to the PGA-16 via a 44-pin high-density D-sub connector, which extends out of the rear of the computer. If you are using an AAF-16 filter, you can connect PGA-16 outputs to AAF-16 inputs either externally via a 26-pin connector or internally via a 34-pin dual-row ribbon-cable connector.
Filter Systems - The PGA-16 plugs into the PC and is programmable through the ISA bus. For large channel count and non-PC based systems, the PGA-16 also fits in a computer chassis that houses multiple boards and is packaged in a rugged case convenient for bench-top or rack-mount applications.
When used as part of the AT-SYS-1000 filter/amplifier system, the PGA-16 is completely remote controlled from a host computer via a serial interface.
Cable Accessories - A variety of cable accessories have been developed for connecting the PGA-16 to any A/D board and to any system. These accessories include BNC connector boxes and cables for inputs and twisted-pair ribbon cables for outputs. Custom accessories also are available.
Screw Terminal Card - The STA-PGA-16 screw termination board provides labeled one-to-one I/O connections for the PGA-16. The STA-PGA-16 uses new Wago connection points, a spring clamping system that reduces wiring time substantially compared to screw-type methods. The clamping force adjusts automatically to wire size, so it provides a reliable contact virtually indepdent of operator skill. The end-result is secure, vibration-proof, maintenance-free clamping every time.
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