Warner Instruments LPF-100B 4-Pole Low Pass Bessel Filter

Warner Instruments LPF-100B 4-Pole Low Pass Bessel Filter
4-Pole low pass Bessel filters with DC Amplifier gains from 1 to 100 LPF DC Amplifier/Filter signal conditioners are used to filter noise and boost signals to levels compatible with computers, chart recorders and tape recorders. Built with analog circuitry, these instruments exhibit very low noise and excellent stability.

• The 4-pole low pass Bessel filter frequencies are selected in six steps
• from 100 Hz to 5 kHz 
• Gains are selectable from 1 to 100 in seven steps, both in 1, 2, 5 sequence. 
• The full 5kHz bandwidth .
• DC signals at the input can be nulled with the Input Offset control. 
• If the gain is set too high for the signal being processed, the Overload indicator will light.

4-Pole Bessel Filter: The filtering capacity if the instrument has been expanded to include a low pass, 4-pole Bessel filter ranging from 0.05 to 20 kHz in 1-2-5 steps. The internal filter can be bypassed for use with external filtering apparatus and allows realization of the instrument’s full 75 kHz bandwidth.

Single & Dual Channel Models
The LPF-100B is a single channel bench top instrument. The LPF-202A is a dual-channel model packaged in a low profile rack mounting cabinet (hardware supplied). Both models have input shorting switches that are handy for quickly establishing a zero level at the input. The LPF-202A also has a digital meter for reading DC or average voltage levels.

Specifications
Input Impedance: 1 MΩ
Input Offset: ±200 mV @ input
Mode: Active and By Pass
Gains: x1, x2, x5, x10, x20, x50, & x100 (1-100)
Input voltage Range: ± 10V
Noise(referred to input): 12 µV RMS DC-5 kHz, 20 µV RMS wideband
Maximum Output voltage: ±10 V
Bandwidth frequency: 10 kHz @ x100 gain
Filter and speed: 4-Pole Bessel low pass
-3 dB Frequencies: 0.1KHz, 0.2KHz, 0.5KHz, 1KHz, 2KHz & 5 kHz
Digital Meter (LPF-100B):
                                           Low Range ±1.999 V
                                           High Range ±19.999 V
Overload Indicator: RED Lights when output exceeds ±10 V
Power Requirements: 100-130 VAC or 220-240 VAC, 50/60 Hz, 3 VA
Physical Size, H x W x D: LPF-100B 9 x 5 x 2.5 inches.

we have LPF 100A and LPF 100B

Audio Output
The BC-535 now sports a VCO circuit providing auditory feedback during membrane formation. This feature is selectable from the front panel and an internal speaker is included. An external speaker output is provided on the instrument rear panel.

I/O
Input and output BNC’s have been duplicated or moved to the instrument rear panel except for those requiring user interaction. Front panel BNC’s include
Command Input, Vc x 10 and Im Output. Rear panel BNC’s include the headstage connecter, Im Output, Cap Sync, Command In, and Gain and Filter telegraphs. A speaker output is also available on the rear panel

Application
The Warners Instrument LPF 100B Low Pass Bessel Filter 4 Pole is a precision electronic filter with several key uses, particularly in fields where signal processing, noise reduction, and frequency control are important. Here are some of the main uses for this type of low-pass Bessel filter:

1. Audio and Audio Signal Processing
Noise Reduction: The LPF 100B is often used in audio applications to eliminate high-frequency noise or unwanted signals from the audio spectrum. It allows low-frequency signals (such as voice or bass) to pass through while filtering out high-frequency components like hiss or interference.
Smoothing Audio Signals: In audio systems, the Bessel filter is favored for its linear phase characteristics, meaning it preserves the waveform of the audio signal more accurately. This makes it particularly useful in high-fidelity audio applications where the integrity of the original signal is crucial.
Crossovers in Audio Systems: The 4-pole low pass filter is ideal for use in audio crossover circuits, where it helps divide an audio signal into separate frequency bands for different speakers (e.g., woofer, mid-range, tweeter) in a sound system.

2. Measurement and Data Acquisition
Signal Conditioning: In laboratory experiments or instrumentation setups, the LPF 100B can be used to filter out high-frequency noise from sensor data or measurement signals. This ensures that the data used for analysis is more accurate and free from high-frequency interference.
Signal Smoothing: When collecting signals from sensors, particularly in systems that generate fluctuating or noisy outputs, a low-pass filter can smooth out rapid oscillations and help isolate the desired frequency band for further analysis or processing.

3. Communications and RF (Radio Frequency) Systems:Filtering in Communication Systems: The LPF 100B can be used in communication systems to filter out higher-frequency noise or to limit the bandwidth of the transmitted signal. It ensures that only the relevant frequencies are transmitted, reducing interference and improving signal quality.Baseband Signal Processing: In radio systems, the low-pass filter can help in the processing of baseband signals, ensuring that high-frequency components do not distort the transmission or reception of the intended signal.

4. Control Systems and Feedback Loops
Filtering Control Signals: Low-pass filters like the LPF 100B are frequently used in control systems to smooth out control signals in feedback loops, ensuring stable operation by filtering out high-frequency noise that could destabilize the system.
Preventing Oscillations in Feedback Systems: In feedback-based control systems (e.g., servos or automation systems), the 4-pole Bessel filter can be used to limit the frequency range of the feedback signal, thereby preventing oscillations and ensuring smooth system operation.

5. Video and Image Processing
Image Signal Processing: In video and image processing, low-pass filters are often used to remove high-frequency noise or aliasing artifacts that may distort visual data. A 4-pole Bessel filter can help achieve a smoother visual signal with fewer unwanted high-frequency components.
Smoothing Video Signals: In high-definition video or imaging systems, the Bessel filter can be used to filter out sharp, high-frequency artifacts while maintaining the integrity of the signal, especially in applications like medical imaging or scientific imaging.

6. Test Equipment and Calibration
Signal Testing and Calibration: The LPF 100B filter is commonly used in test equipment to simulate ideal signal conditions or to calibrate systems by removing unwanted high-frequency noise. It ensures that instruments receive clean signals within a defined bandwidth for accurate measurements.
Time-Domain Analysis: When working with time-domain signals, the Bessel filter can help to eliminate high-frequency spikes that might skew the results of time-based analysis, allowing for a more precise observation of the signal’s lower-frequency behaviour.

7. Power Supply Filtering
Power Supply Noise Reduction: In power supply circuits, low-pass filters are used to reduce ripple and high-frequency noise, ensuring that the output voltage remains stable and clean. This is crucial for sensitive electronics, particularly in medical devices or high-precision laboratory equipment.

8. Scientific and Research Applications
Experimental Setups: In scientific experiments where accurate signal measurement is required, the LPF 100B helps filter out any unwanted high-frequency components from experimental data. It is especially useful in research involving analog signals, sensor outputs, or signal processing systems.
Spectral Analysis: When conducting spectral analysis of a signal, the filter can be used to isolate specific frequency ranges of interest, excluding high-frequency noise that could obscure the results.

9. Audio and Signal Simulation
Signal Simulation and Testing: In audio design and signal processing testing, low-pass filters are often used to simulate the effects of bandwidth-limited signals. The LPF 100B is ideal for such applications, as its 4-pole design ensures sharp cutoff characteristics while maintaining minimal distortion.