VBF40 Electronic Filter

The VBF40 is one of Kemo’s most versatile filters and sits at the top end of its range alongside the VBF44 electronic filter. The VBF40 offers up to 16 channels in one chassis, all with exceptional user functionality.

1 Hz – 255 kHz x1000 (+60 dB) Gain 5 built in Filter Responses

Range Topping Versatile Filter / Amplifier System

  • Filter cutoff range 1 Hz to 255 kHz
  • Flexible Gain x1 to x1000 (+60dB)
  • 5 built-in filter responses
    2 lowpass, 2 highpass, and Bandpass
  • Sharp 135 dB / Octave filters
  • Precise channel matching
  • IEPE Inputs
  • Series / Parallel connection
    between channel pairs
  • Manual and computer control
  • Easy to use
  • 2-16 channels per rack
  • Signal level indication
  • Rack mounting
  • Wide Dynamic Range

The Kemo VBF40 electronic filter combines programmable amplification and high performance analogue filtering in a versatile easy-to-use package. Ideally suited to today’s hard-working flexible data capture and analysis applications. The VBF40 electronic filter has a unique combination of input gain, 5 built in filter responses, and output gain. This combination makes the VBF40 electronic filter a flexible signal filtering and amplification unit with capabilities suited to a wide range of applications. Built in series and paralell conection between channels allows a fully variable Bandpass, notch and band stop filters to be configured.
The VBF40 is available as a full width 19″ rack with up to 16 channels and a compact 4 channel VBF44 unit. Stainless steel front panels, passive cooling, easy to use front panel controls, BNC input/output front panel connectors, and a very versatile set of filter responses are among the details which make the VBF40 electronic filter a top of the range laboratory filter.

Summary Specification
Channels 2 – 16 per rack
Control Manual LCD and push button
Ethernet FICL II interface
Frequency DC – 255 kHz (4 ranges)
Bandwidth > 1 MHz,  1V signal, 0dB gain, highpass filter and filter bypass
Input Gain  x1, x2 (+6dB), x5 (+14dB), x10 (+20dB), x20 (+26dB), x50 (+34dB), x100(+40dB)
Output Gain   x1, x2 (+6dB), x5 (+14dB), x10 (+20dB)
Filters  5 Switchable; 2 Lowpass, 2 Highpass, Bandpass, and Filter Bypass
Filter Responses  L1, L2, H1, H2, B1
Input Coupling  AC / DC / IEPE (4mA 24V) with 3 stage LED indicator
Input Mode Single ended or differential
Signal level  +/- 10V pk-pk (usually with ‘headroom’)
Signal Level Indication 4 colour level LED on front panel
Size 145 x 482 x 420 (3U 19″ x 16″)
Power 90 -120 / 180-240 Vac 50/60Hz

Flexible Input

The input may be AC or DC coupled. The input may be switched between single ended or differential inputs. Note the AC Coupling is matched on both the signal hot and signal cold inputs on the differential input setting.
There is a switchable 4mA IEPE source. Inputs and outputs are BNC connectors, mounted on the front panel.

Frequency Range 1Hz to 255kHz

The VBF40 channels can be independently to frequencies between 1Hz and 255kHz in four 255:1 ranges. 1Hz – 255Hz, 10Hz – 2 550Hz, 100Hz – 25.5kHz, and 1kHz – 255kHz.

Gain Range and Signal Indication

Each channel has up to x 1000 (+60dB) gain. x 100 (+40dB) before the filter, and x 10 (+20dB) after the filter.
There is a signal level indication LED fitted to each channel between the input gain stages and the filter.
Signal level indication – 0%- off -10% – green – 70% – orange – 95% – red.
Each channel has an overall overload indicator on the input.

Lowpass / Highpass and Series / Parallel

Each channel can be independently set to high or low pass, over the range 1 Hz to 255 kHz.
Pairs of adjacent channels can be operated in series or parallel modes. In series mode this gives fully variable Bandpass filtering.
In parallel mode the channels can be set to give Bandstop or notch filtering.
this feature of the VBF40 series allows for a massive range of Bandpass, notch and Bandstop filters to be set.

5 Filter Responses

Each channel has 5 filter responses, sharp lowpass, sharp highpass, time optimised lowpass, time optimised highpass, and a Bandpass filter response. The filter stage can be bypassed, so the unit can be used as an amplification stage only.


The versatility of the VBF40 makes the application area very large. They include, classic anti-Aliasing, random noise conditioning, all types of mechanical testing, audio work, medical signals, seismic and geological signals, SONAR and oceanographic, military and a wide range of others.

Response Versatility

Each VBF40 channel can be switched to five different filter responses to suit the application. 2 lowpass filter responses, 2 highpass filter responses and one Bandpass filter for each channel.
The 5 filter characteristics are:
Flat to Fc -80 dB at 1.5 Fc
Flat to 0.6 Fc -3 dB at Fc -96 dB at 4 Fc linear phase
Flat from Fc -80 dB at 0.67 Fc
Flat from 1.67 Fc -3 dB at Fc -96 dB at 0.25 Fc
Flat at Fc -3 dB at 1.06, 0.9 Fc -35 dB at 1.5, 0.67 Fc
The filter may also be switched out completely.

Ease Of Use

The VBF40 has large easy to use push buttons with menu driven control via the LCD display.

Interface and Channel Addressing

The VBF40 electronic filter has the updated Kemo FICL II text over Ethernet interface. The user is given full control of all the functions, the VBF40 does not think for itself.

The interface can control up to 64 channels, each rack can be easily configured as a ‘slave’ unit. In theory an infinite number of slaves can be connected to make a system with many racks. Each filter card can have its control address set by on board DIP switches, each card is a ‘listen only’ device in the control system. This means cards can share the same control address, and the cards sharing the same address will all be set to exactly the same settings. This gives interesting possibilities, especially if all channels in a system will always be set to the same settings. Only one set of commands either from the front panel or from the interface need be used. One VBF40 frame can control a total of 64 channels if needed.

Block Diagram

This shows the generic block diagram for a Kemo 40 series filter channel.

Related Systems

The VBF40 is part of a range of filters.
The VBF44 is a 4 channel system, with channel grouping and tracking functions which make it ideal for twin sensor applications.

Price/Performance Ratio

Due to its versatility the VBF 40 range offers significant price performance advantages over similar filter systems. Tremendous care has been taken to ensure repeatable and dependable performance.

For more information please contact us.

Subscribe To Our Newsletter

Join our mailing list to receive the latest news and updates from our team.

You have Successfully Subscribed!