The VBF 44 is our top of the range 4 channel laboratory filter, with versatile channel tracking and grouping modes, gain, and 5 built in filter responses.

Filter cutoff ranmge 1 Hz - 255 kHz Gain -20 to +70 dB 5 Built in Filter Responses 2 Lowpass, 2 Highpass, and Bandpass 135 dB/Octave filters Manual and computer control Easy to use Wide dynamic range 'Stereo' and 'Track' filter tuning modes   VBF 44 pdf data sheet (86 kB)   Order Now

The Kemo VBF44 is a benchtop filter offering unparalleled versatility. It contains 4 precision electronic filter channels. Each filter channel can be used independently to produce a 4 channel programmable filter/amplifier, or in pairs to produce 2 channels of bandpass, bandstop and other composite filters of many kinds. The VBF 44 is now built in a compact stainless steel chassis and stainless steel laser cut rear panel, with upgraded system cooling.

Easy to use front panel controls, BNC input/output connectors, and a very versatile set of filter responses make the VBF 44 a top range laboratory filter.

Summary Specification

Channels	4
Control	Menu driven LED and thumbwheel  RS232 standard, Optional GPIB
Frequency	1 Hz - 255 kHz (4 ranges)
Bandwidth	> 1 MHz  1 volt signal, 0 dB gain, filter highpass and bypass
Input Gain	0 dB to +40 dB, in 20 dB steps, with switchable -10 dB attenuator
Output Gain	-10 dB to + 30 dB in 2 dB steps
Filters	5 Switchable; 2 Lowpass / 2 Highpass and Bandpass
Filter Responses	L1, L2, H1, H2, B1
Input Coupling	AC / DC
Input Type	Single ended / Differential
Size	210 x 445 x 74mm ( 8.3” x 17.5” x 3.0”)
Power	90 -120 / 180-240 Vac 50/60Hz

Frequency Range
Each filter in the VBF44 tunes over a frequency range of 1 Hz to 255 kHz in four decade ranges. A low frequency version with 0.01 Hz to 10 kHz range is also available.

Gain Range
The inputs (differential, switchable to single ended) have gain to +40 dB and the output stages provide -10 dB to 30 dB. In dual 2 channel mode signals are connected to two pairs of BNCs on the front panel; the two filters in one group share input and output amplifiers to minimise the building up of errors. In 4 channel mode signals are connected to rear panel BNC connectors.

A Flexible Response
Even in 4 channel mode, each filter in the VBF44 offers five responses - high slope elliptic lowpass and highpass, flat passband linear phase lowpass and fast settling highpass, and bandpass with characteristics similar to 1/3 octave. The filter can also be bypassed and the unit used as a programmable amplifier.

Keeping in Tune
All VBF44 parameters are displayed on large, bright LED digits and are adjusted with a rotary control and push buttons. All selections are non-volatile, and 3 complete set-ups can be stored and recalled when needed. Plug-in GPIB and RS232 interface cards are available, and all digital circuitry is opto-isolated from the signal path.
Several tuning methods are provided to simplify the application of the VBF44 in the dual 2 channel mode. Cutoff frequencies can be 'locked together' once the desired composite filter shape has been set. Subsequent adjustment of the reference channel cutoff frequency will cause the other channel to retune automatically to preserve the selected response shape. This is called 'tracking' mode and is invaluable for tuneable bandpass and bandstop filters.
In 'stereo' mode the instrument sets two identical composite channels, useful for audio signals and quadrature baseband signals in image processing, SONAR, and Doppler studies. These modes can be used manually and through the computer interfaces.

Easy Connections


The VBF 44 is easy to use and connect to, all 4 channel connectors are available on the laser cut and marked rear panel.