For professionals working in signal-dependent industries in the frequency range of 0.03Hz to 1MHz, precision and reliability are essential. The Model 3988 is designed to simplify the process of isolating and analyzing specific signals with accuracy and ease. Engineered for versatility across a wide range of applications, this advanced instrument streamlines signal access and enhances efficiency in any technical environment. Explore how the Model 3988 can make your work simpler, faster, and more precise—no matter your field.

What Is the Model 3988?

The Model 3988 Dual-Channel Filter from Krohn-Hite Corporation combines precision engineering with versatility, delivering superior performance across a wide range of signal processing applications.

Supporting both Butterworth and Bessel filter types, the Model 3988 provides users with exceptional flexibility—ideal for professionals in engineering, biomedical, environmental, acoustic, and geophysical fields.

General Specifications

• Filter Types: Selectable Butterworth and Bessel
• Frequency Range:
• Low-Pass: Tunable 03Hz to 1MHz
• High-Pass: Tunable 03Hz to 300kHz
• Optional 3988-002: Change low end frequency is lowered to003Hz
• Attenuation Slope: 48dB/octave (8-pole)
• Input Types: Selectable Differential or single-ended
• Coupling: Selectable AC or DC

Input Specifications

• Input Impedance: 1MΩ (differential), 500kΩ (single-ended)
• Pre-Filter (Input) Gain: Up to 50dB in 10dB steps
• Maximum Input Voltage: ±10V peak

Output Specifications

• Output Impedance: 50Ω
• Post-Filter (Output) Gain: Up to 20dB in 1dB steps
• Maximum Output Voltage: ±10V peak
• Offset Voltage: Adjustable to ±10V
• Power and Physical Specifications
• Power Requirements: 100–240V AC, 50–60Hz
• Power Consumption: 30W
• Dimensions: 5″ H × 8.5″ W × 13.5″ D (89mm × 216mm × 343mm)
• Weight: 10lbs (4.5kg)
• Environmental Specifications
• Operating Temperature: 0°C to 50°C
• Storage Temperature: −40°C to 75°C
• Humidity: Up to 95% non-condensing

Common Applications

• Random Noise Testing – Effectively filters out unwanted noise, providing clarity in precision testing
• Ultrasound Testing – Ideal for medical and industrial use, filtering high-frequency signals with
• Biomedical Applications – Perfect for analyzing ECG and EEG signals, ensuring clean, accurate
• Vibration Analysis – Provides high accuracy for assessing mechanical vibrations, aiding in diagnostics and maintenance.
• Environmental Monitoring – Enables accurate analysis of environmental data such as seismic or atmospheric activity.
• Audio Communications – Enhances signal purity for optimal sound quality in professional communication systems.

What Sets the Model 3988 Apart

The Model 3988 stands out for its dual-channel design, allowing simultaneous independent filtering or combined use for enhanced band-pass or band-reject operation. With a broad frequency range from 0.03Hz to 1MHz (extendable to 0.003Hz), it offers unmatched flexibility for diverse signal environments.

Its programmable memory feature enables storage of up to 99 filter setups, allowing rapid recall of configurations and saving valuable setup time. Precision is further ensured with 48dB per octave attenuation, while pre-filter (input) gain control up to 50dB (in 10dB steps) and post-filter (output) gain control up to 20dB in 0.1dB steps offers optimum flexibility for pre- and post-filter adjustments.

Using the Model 3988

Integrating the Model 3988 into your workflow is straightforward:

• Set up the device securely on a bench and connect it to
• Connect inputs and outputs using either differential or single-ended
• Select your filter type and frequency using the front-panel controls for Butterworth or Bessel
• Adjust gain levels as needed, utilizing pre- and post-filter gain
• Fine-tune the output by testing different signal settings to achieve optimal

Why Choose Krohn-Hite

For over 75 years, Krohn-Hite Corporation has been a leader in precision test and measurement instrumentation. Founded in 1949, we continue to uphold our legacy of innovation, quality, and reliability. The Model 3988 Dual-Channel Filter reflects this commitment — delivering advanced filtering solutions that meet and exceed the demands of today’s professionals.