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16-Channel Anti-Alias Low-Pass Filter Card for Signal Conditioning in Data Acquisition Systems

Features

• Programmable anti-alias low-pass filter on each of 16 channels
• Cutoff frequency ranges between 2 Hz and 200 kHz
• 8-pole Bessel, Butterworth, Cauer, high-speed Cauer, or high-speed linear phase filters
• > 120 dB/octave rolloff
• ±10V input and output
• Automatic DC offset compensation
• Synchronized sampling-clock output to eliminate the need for post-filter
• Driver software for Windows 3.1/95/Me/NT/2000/XP, DOS, LabVIEW, HP VEE
• Menu-driven software with easy-to-use graphical interface
• Computer chassis houses one or many boards for non-PC based or high channel count systems

Options

• Instrumentation amplifier card with differential input
• Software-programmable gains of 0.5, 1, 2, 5, 10, 20, 50, 100, 200, 500, and 1,000
• Programmable AC/DC coupling
• Analog pre-filters for clock-aliasing protection
• Post-filters for waveform reconstruction if A/D is unsynchronized

Overview

The AAF-16 is a 16-channel anti-alias low-pass filter card series for front-end signal conditioning in PC-based data acquisition systems. Each channel uses any one of five 8-pole filter types with a rolloff of up to 120 dB/octave and a variable cutoff frequency range between 2 Hz and 200 kHz. The cutoff frequency can be set using 2 on-board programmable sources or 2 external sources, allowing for 4 different cutoffs on each AAF-16. Each channel can be individually bypassed, routing the input signal directly to the A/D.

Pre- and post-filters on the optional PPF add-on module as well as the standard built-in pacer clock allow the AAF-16 to offer superior specifications that meet the maximum performance needed by high-resolution A/D converters. When used with the PPF, the switched-capacitor AAF-16 becomes a hybrid filter that offers the advantages of programmability, tunability and low cost while matching the performance of traditional, continuous time active filters.

Support Software

Alligator Technologies has developed both menu-driven and driver-level software for controlling the functions on the AAF-16.

Menu-Driven Software - The AAF-16 is supplied with WSETAF16 for Windows 3.1/95/NT and the menu-driven SETAAF16 for DOS, which are software programs that do not require programming. With a few simple mouse clicks, you can use this software to control the board's filter type, filter mode, clock source, actual cutoff frequency and pacer clock.

The installation program for the Windows 95 and NT versions of the AAF-16's software automatically creates a WSETAAF16 Ä Alligator Technologies program group. Double-clicking on the WSETAAF16 program item opens a single setup screen which contains pop-up menus for selecting key parameters. For example, the filter mode can be specified for each group of 4 channels. The setup screen also includes the board address, which address specifies the memory location used by the computer to communicate with the board; the clock source A and clock source B values, which can be used to control the cutoff frequency; and the integer divisor of the pacer clock, which synchronizes A/D sampling with the AAF-16 filter clock.  After setting the desired parameters, pressing F10 in SETAAF16 or clicking on "Program Board" in WSETAAF16 will program the board located at the I/O address specified in the board address field.

Once selected, the desired parameters can be saved as an AAF-16 description file (ADF). Once saved, the settings stored in this file can be easily applied to other boards by selecting and loading the file.

Function Libraries- If you prefer to develop your own programs, the AAF-16 comes with DOS and Windows linkable libraries that provide more than 10 functions for configuring and controlling the AAF-16. The set_ group of subroutines modifies the Board Configuration Structure values, which are then used by the program_ group of subroutines to create and send the data control words required by the AAF-16.

Example application programs are provided for popular compilers, including Visual C++, Visual Basic, Borland C++, and Borland Pascal.

LabVIEW Driver - AAF16.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.

Options

PPF Pre- and Post-Filtering Module

The PPF is an add-on module that plugs into the AAF-16 and provides 8 channels of pre - and/or post-filtering. It features a 2-pole Butterworth filter with fixed frequencies at any point in the entire spectrum of the AAF-16's frequency selection.

PGA-16 Programmable Gain Card

The PGA-16 is a 16-channel instrumentation amplifier card designed to provide differential inputs, programmable AC or DC coupling, and pre-filter gain to the AAF-16. Each channel can programmed independently for a gain of 0.5, 1, 2, 5, 10, 20, 50, 100, 200, 500, or 1,000.

Connection to Your Data Acquisition System

All I/O connections from the AAF-16 are made via two 26-pin high-density D-sub connectors that extend out of the rear of the computer.

Filter Systems - The AAF-16 plugs into the PC and is programmable through the ISA bus via menu-driven or driver software. For large channel count and non-PC based systems, the AAF-16 also fits in an external 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 AAF-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 AAF-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-AAF-16 screw termination board provides labeled one-to-one I/O connections for the AAF-16. The STA-AAF-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.

How to Order

• AAF-16 - Programmable, 16-channel low-pass filter card for PC/AT (ISA) data acquisition systems

• PPF - 8-channel add-on module with 2-pole pre- and post-filters

• PGA-16 - Instrumentation amplifier card with programmable AC or DC coupling and differential inputs

• Accessories - See a data sheet on our cable accessories.
  • AT-BNC-16/I - Standard BNC connector box with 18" cable for AAF-16 input
  • CK-A16 - I/O connector kit with two DB-26
  • STA-AAF-16 - Screw termination planel for AAF-16
    • CAT-A16-I - Shielded cable for AAF-16 input only to STA-AAF-16, 0.5m
    • CA-A16-O - Shielded cable for AAF-16 output only to STA-AAF-16, 0.5m
  • CA61-x - Twisted-pair ribbon cable for AAF-16 input to open end, specify length (x) in 0.25m
  • CA62-x - Twisted-pair ribbon cable for AAF-16 output to open end, specify length (x) in 0.25m
  • CA63-x-y - Twisted-pair ribbon cable for connecting AAF-16 output to any A/D card (input only), specify length (x) in 0.25m and A/D card (y)
  • CA64-x-y - Twisted-pair ribbon cable for connecting AAF-16 input from any source, specify length (x) in 0.25m and source connector (y)
  • CA66-PGA16 - PGA-16 output to AAF-16 input interconnect cable
  • CA69-x-y-z - Twisted-pair ribbon "y" cable for connecting AAF-16 output to any A/D card with a single input/output connector; specify length (x)  in 0.25m, A/D card (y), and A/D-output source connector (z)

Related Pages

• Simplify your system connections.  Check out our list of Cable Accessories.
• Need help selecting the best filter type for your application? Check out our Filter Type Selection Guide.
• What is aliasing and how do filters eliminate its effects to ensure more accurate results?  Find out in our Low-Pass Filter Tutorial.

PHONE 949-515-1400        FAX 949-515-4724       E-MAIL productinfo@alligatortech.com

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