The VBF 42 is our top of the range 2 channel laboratory filter/amplifier, with gain, 5 built in filter responses, easy control, and versatile filter configurations. 

Filter cutoff range 1Hz to 255kHz Gain -20dB to +70dB 5 built-in filter responses 2 Lowpass, 2 Highpass, and Bandpass 135 dB / Octave filters Separate / series / parallel modes Manual and RS232 (FICL) control Non-volatile setup storage Wide dynamic range   VBF 42 pdf data sheet (70 kB)   Order Now

The VBF42 variable filter offers high performance and a wide range of features in a compact 1U case. Care has been taken to maximise ease-of use resulting in a simple, uncluttered front panel design and crisp, bright back-lit LCD display for all parameters.

The two filter channels can be independently controlled as well as internally connected in series or parallel. To implement a wide range of bandpass and bandstop filters, as well as independent lowpass and highpass channels.

Summary Specification

Channels	2
Control	Menu driven LCD and thumbwheel RS232, FICL text based control
Frequency	1 Hz - 255 kHz (4 ranges)
Bandwidth	> 1MHz, 1 Volt signal, 0dB 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	1U 19"
Power	90 -120 / 180-240 Vac 50/60Hz

Frequency Range
All VBF42 channels can be programmed to provide cutoff frequencies between 1Hz and 255kHz in four 255:1 ranges. 

Gain Range
The gain of each channel can be programmed between -20dB and + 70dB in 2dB steps (including the switchable 10dB input attenuator). Up to 40dB of gain is available before the filter, the rest is post-filter. Input overload monitor LEDs are visible on the front panel. Input AC coupling may be selected if desired.
The inputs are differential, with a front panel switch to convert them to single-ended. Inputs and outputs are BNC, mounted on the front panel.

Series / Parallel Operation
The two channels of the VBF 42 can be used in three connection modes:-
Separately - each filter operates independently of the other.
Series - the signal enters channel 1 and then channel 2 in series, this is used for bandpass filtering, and 'double strength' filtering using both filters set the same.
Parallel - the two channels operate in parallel, this used for band stop and notch filtering.
The use of series and parallel filter connection, with the 5 filter types, and the gain, give for a very versatile set of filter shapes and possibilities from the VBF 42.

+	+	+	+
Lowpass and separate Lowpass	Highpass and separate Highpass	Lowpass and separate Highpass	Highpass and separate Lowpass

 

Highpass and Lowpass in series = Bandpass	Lowpass and modified Lowpass in series =  true double strength filtering

 

Highpass and Lowpass in parallel = Bandstop	Highpass and Lowpass in parallel = narrow Bandstop (Notch)

All the curves above were measured on a standard Kemo filter, by using a combination of the series/parallel control and the filter response modifiers.

Response Shapes
Each channel in the VBF42 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. Using the filters as a pair, either in series or parallel, allows a huge number of combinations (we make it around 130 million) for extracting, rejecting or band-limiting signals.

The combination of series or parallel connection of the VBF 42 channels, coupled with the 5 filter responses allows some very complex filter combinations. 

Operational Features
All parameters are controlled using three 'menu' buttons and a rotary control. Both the filter amplifiers and the interface settings are controlled in this way. All settings are non-volatile, and on power-up the unit returns to the last programmed state. Up to nine complete sets of setup information may be stored and recalled at any time. 'Ratio Tuning' enables filter channels to be tuned with a constant ratio between cutoff frequencies (ideal for bandpass and notch use)

External Control
The VBF 42M uses the Kemo FICL RS232 interface for external control. This uses simple text based commands sent via RS232. It is easy to implement and control the VBF 42 from an external RS232 controller.

Kemo VBF 40 Series
The VBF42 is another product in a range of high performance variable active filters which includes the VBF44, a 4 channel version of the VBF42, and the VBF40, a multichannel version, with the same electronic performance.

  VBF 42 pdf data sheet (70 kB)      Order Now