space saving 1U case cutoff range 0.01Hz... 99.9kHz simple front panel operation ANSI Class III 1/3 octave bandpass response complementary bandstop mode bandpass/bandstop switchable

The VBF18 is a true adjustable bandpass and bandstop filter, which can be fitted with one or two signal channels each of which can be freely switched from bandpass to bandstop mode. The VBF18 is closely related to the BenchMaster VBF8 2 channel lowpass/highpass filter but is designed to offer sharp bandpass and band elimination responses from each of its individual channels.

Frequency Range 0.01Hz to 99.9kHz
The VBF18 offers a cutoff frequency range of 0.01Hz to 99.9kHz, covered by five three-digit ranges. Frequency is set with three rotary decade switches and a range switch.

ANSI Class III 1/3 Octave Bandpass
When switched to bandpass mode, the VBF18 signal channel is fully compliant with international specifications for 1/3 octave filters and the three digit resolution of frequency setting allows all standard band centres to be set.
The response shape is designed to offer a true 1/3 octave noise bandwidth. When fed with white noise, the bandpass filter will give the same rms output as an ideal (rectangular) filter 1/3 octave wide. Response at the interband points is typically -4.1dB, and at the adjacent band centres it is -23dB. The filter passband has a theoretical ripple of ±0.1dB f or frequencies ±6% from the indicated frequency of the filter.

1/3 Octave Bandstop Response
When switched to bandstop mode, the VBF18 filter provides a notch filter with theoretical ripple in upper and lower passbands of ±0.1dB. The response of the filter is typically 1dB down at points one sixth of an octave either side of the selected cutoff frequency, and typically greater than 50dB down in a region ±2% from the notch centre (which is typically accurate to ±1% from the indicated cutoff point).

Summary Specification

Channels	2
Control	Manual Front panel all functions  Optional GPIB
Frequency	0.01 Hz - 99.9 kHz
Gain	0, +10 dB, +20 dB ( x1, x3.1, x10)
Filters	1/3rd Octave Bandpass, Bandstop
Filter Responses	1/3rd Octave Bandpass, Bandstop
Input Coupling	AC / DC
IEPE	Yes 4mA 20V
Size	1U 19"
Power	90 -120 / 180-240 Vac 50/60Hz  Optional 9 - 30 V DC, with AC 'power brick'

Easy Manual Control
The VBF18 is designed primarily for manual use. A front panel switch connects the control lines of the two channels allowing a tracking mode in which channel 2 follows the settings of channel 1.