GSAF high precision low pass anti alias filter for data acquisition

GSAF-10

Precision Analog Anti-Alias Low-Pass Filter Board for Front-End Signal Conditioning With 16-Bit and 18-Bit A/D Converters in Data Acquisition Systems

Features

One independent anti-alias low-pass filter channel with differential input
96 dB (typ) common-mode rejection
Gain 1.0 ± .001dB
Adjustable DC offset trim to 1.0 mV
Perfectly suited for 16-bit A/Ds - lowest offset and gain errors equate to less than ±2 LSB
Extremely low THD
9-pole low-pass Butterworth and Bessel filter transfer functions
Standard corner frequencies: 1.0 kHz, 2.0 kHz, 5.0 kHz, 10.0 kHz, 20.0 kHz, and 50 kHz
- Custom corner frequencies to customer specification also available
Input and output protection
Offset guaranteed to less than ±300 microV
Offset drift ±15 microV typical
Adjustable DC offset trim to 0.0V ±15microV
Adjustable gain trim to 0.0dB

Overview

The GSAF-10 Gold Series are analog low-pass filter boards that offer the performance required to maintain the maximum accuracy of high-precision 16- and 18-bit A/D converters. Lowest offset and gain errors equate to less than ±2 LSB over time and temperature, guaranteeing full dynamic range of conversion (no missing bits).

Each board provides one differential-input channel with a common-mode rejection ratio of 96dB (typ) for maximum rejection of signal interference. Total harmonic distortion with a 1 kHz 20 vpp input signal is a very low .002%.

The GSAF-10 Gold Series are factory-set to a standard -3 dB corner frequency of 1.0 kHz, 2.0 kHz, 5.0 kHz, 10.0 kHz, 20.0 kHz, or 50 kHz. Custom-built filters with user-specified fixed corner frequencies tuned by the factory or tunable low-pass filters with adjustable cutoff frequency ranges are optionally available.

The GSAF-10 are available with differential-input 9-pole low-pass Butterworth and Bessel filter transfer functions with 54 dB/octave roll-offs; The Butterworth model provides the maximally flat passband response and sharp cut-offs required in such applications as anti-aliasing and noise reduction. The Bessel model provides the linear phase characteristics, uniform group delay, and monotonic roll-off required for such applications as closed-loop systems and signal reconstruction.

A feedback topology at the output stage provides for a 10 mW output impedance, making the GSAF-10 capable of driving any A/D converter input stage without further buffering. Input impedance is 20kOhms ±2%.

Pre-installed offset trimming and output-gain scaling potentiometers permit nulling of offset and gain for expansion of dynamic range for maximum resolution. Both adjustments are incorporated at the last stage of the filter to compensate for all filter component variations and are accessible at the board's edge.

Connection to Your Data Acquisition System

The GSAF-10 can be mounted anywhere on the lab bench with stand offs. For multi-channel systems, the GSAF-10 can be plugged into a standard 19" rackmount such as the LS-100R or LS-101 system. They also can be used in a VME chassis with other VME/VXI-based boards.

The GSAF-10 requires a ±15V power supply, which is obtained from a built-in power connector for stand-alone operation or from the included motherboard connector for rackmount applications.

How to Order

GSAF-10/x-y - Precision analog low-pass filter board for 16-bit and higher A/D converters. Specify 9-pole filter transfer function (x) either B for Butterworth or L for Bessel and corner frequency (y).

Related Pages

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.

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