Versatile 2 Channel Filter Amplifier
- 2 Independent Channels each switchable high / low pass
- Highpass / Lowpass / BandPass / Bandstop and Notch in one instrument
- 0.01Hz - 99.9kHz filter range
- Ethernet based interface (option)
- Simple front panel operation
- Input gain to x 500(+54dB)
- Signal level indication
- Switchable filter modifiers
- Six models
Incredible Featuring Creates Multiple Benchtop Capabilities In A Single Unit
The BenchMaster 8 series of variable filters are now in their 6th generation, two channels of high performance analogue filter, plenty of gain, signal level indication, and flexible input front end all in a compact, solid 1U high package. This versatile instrument has set the standards for laboratory and industrial filtering, providing a reliable general purpose filter amplifier with a frequency range, and filter responses to suit virtually all applications. BenchMaster 8's use specially manufactured components to ensure close tolerances and good channel matching. The latest version is a complete redesign, giving improvements in signal to noise ratios, overall noise, and a clearer front panel. Modern manufacturing techniques allow us to offer quick deliveries. The BenchMaster 8 uses no fans, and is silent in operation.
|Channels||2 per unit (independent)|
|Control||All functions by front panel switches.
Optional External control, 10BaseT text based FICL II interface.
|Frequency||0.01 Hz to 99.9 kHz, in 5 ranges|
|Gain||1, 2, 5, 10, 20, 50, 100, 200, 500, (+54 dB)|
|Filters||Switchable highpass / Lowpass|
|Filter Responses||6 types. 4 and 8 Pole Butterworth 03, 05 , 4 and 8 Pole Bessel 07, 09,(see note) General Purpose 41, and Sharp Elliptic 13.|
|Filter Modifiers||Flat, Butterworth, Pulse ( not all operate with all filter responses)|
|Input Coupling||AC / DC ( Matched AC coupling on Differential Input)|
|Input Mode||Single Ended / Differential|
|Input Overload||Absolute Input overload indication (single ended or differential)|
|IEPE||4mA 24V current source|
|Signal Level||+/- 10 V pk-pk. (Usually with 'headroom')|
|Signal Offsets||+/- 50% on output, +/- 50% on output single ended only. Factory fitted option.|
|Signal Level Indication||3 colour, 4 signal level, off / green / yellow / red|
|Power||90 -120 / 180-240 Vac 50/60Hz
Optional 9 - 30 V DC, with AC 'power brick'
Frequency Range 0.01Hz to 99.9kHz
The BenchMaster 8 offers a cut-off 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.
Lowpass / Highpass
Each channel can be independently set to high or low pass, over the range 0.01 Hz to 99.9 kHz.
Single ended or differential input can be set, with overload indication on the input signals. Input signals can be DC or AC coupled, with matched coupling for AC differential input. A 24V DC 4mA source for IEPE transducers is provided, with LED indication of correct operation of the transducer. Green shows correct operation, red shows short circuit, and nothing indicates open circuit.
The BenchMaster 8 has two stages of input gain, x1, 2, 5 (0,+6,+14 dB), as precision differential amplification controlled as one front panel switch, then x 1, 10, 100 (0,+20,+40 dB) as a separate switch control. This combination is easy to use and allows amplification of small signals. The amplification is applied to the signal before the filter stages. The filter stages can be bypassed, so the BenchMaster 8 can be used as a pure amplifier, and if required the two channels can be linked in series to give x 250 000 (+108 dB) gain.
Signal Level Indication
BenchMaster 8 filters have 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.
Three Switchable Response Modifiers
Each BenchMaster 8 has 3 filter modifier settings:-
Butterworth - provides a -3dB at cut off type response, the normal operating position for the Butterworth response 8.03 and 8.05.
Flat - a flattened amplitude response up to the cut-off frequency, the normal operating position for responses 8.13 and 8.41.
Pulse - a minimum overshoot response, the normal operating position for the Bessel response 8.07 and 8.09.
The use of these modifiers makes for a very versatile filter, especially when coupled with the Series/Parallel mode. For Butterworth filters (8.03 and 8.05) the use of the flat setting allows 2 filters in series to provide correct shape double strength filters. Without these modifiers 2 Butterworth filters in series would have -6dB at cut off, but with one filter in the series, set to 'flat' the correct -3 dB at cutoff is maintained. This allows 96 dB/octave Butterworth filters to be set on a BenchMaster 8.03.
NOTE not all modifiers work with all filter responses.
Series / Parallel Operation
The two channels of the BenchMaster 8 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 filter modifiers and the gain, give for a very versatile set of filter shapes and possibilities from the BenchMaster 8.
|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 BenchMaster 8.03, by using a combination of the series/parallel control and the filter response modifiers.
Easy Manual Control
The BenchMaster 8 is designed for easy manual operation. The controls are laid out in an easy to understand logical way. All manual controls are on the laser cut and laser etched front panel. Bearings are fitted to the control knobs to ensure smooth long life operation. In most cases the operation of the BenchMaster 8 is intuitive. Some of us at Kemo have been filter users, we have used Kemo products on site late at night cold and tired, so we like to keep things simple and easy to operate.
Block Diagram of BenchMaster 8
|Optional External Control
BenchMaster 8 units are fitted with control logic for the optional Kemo
freq,1,250 - sets channel 1, frequency to value 250
Typical response time to send commands to one channel and implement the settings is about 200mS. The RDBK files can be stored as text files, so test setups can be stored for measurement audit purposes.
Six Models, Six Filter Responses
BenchMaster 8.05 - 4 Pole Butterworth response 24 dB/Octave. ( Data sheet Response 8.05 )
BenchMaster 8.03 - 8 Pole Butterworth response 48dB/Octave. ( Data sheet Response 8.03 )
BenchMaster 8.09 - 4 Pole Bessel response NOTE the filter modifiers Flat and Butterworth are not available with this response
BenchMaster 8.07 - 8 Pole Bessel response NOTE the filter modifiers Flat and Butterworth are not available with this response
BenchMaster 8.41 - General Purpose, very flat to cut off, linear phase.
BenchMaster 8.13 - Sharp Elliptic type filter. -93dB at twice cutoff. ( Data sheet Response 8.13 )
Amplitude click for larger images Phase
Optional DC Power
9-30V DC input is available as an option. Power input by 'XLR' type connector, with an AC 'power brick' to power the unit from mains when available.
Please check our page about DC Power.
The BenchMaster 8 is manufactured using the latest surface mount technology, independent linear power supplies for the logic and analogue circuits. The BenchMaster 8 is housed in a solid aluminium case, ready for rack mounting, and with handles which protect the front panel controls. The front panel is laser cut and marked stainless steel, and most of the internal and external fasteners are stainless steel, vibration resistant where possible. It is even possible to turn off the LED indicators, for use in dark optical laboratories. This latest version is a complete redesign, and one that all the staff at Kemo have contributed to, it is a product we feel proud of, and after over 40 years of building filters one that has considerable expertise built into it.
Please order as:-
BenchMaster 8.05, 4 pole Butterworth
BenchMaster 8.03, 8 pole Butterworth
BenchMaster 8.09, 4 pole Bessel
BenchMaster 8.07, 8 pole Bessel
BenchMaster 8.13, 8 pole sharp anti-aliasing type filter
BenchMaster 8.41, 8 pole general purpose linear phase filter
SPECIAL NOTE - a BenchMaster 8 can be supplied with any two filters from the above selection, so a unit can be supplied with one 8.03 channel and one 8.41 channel.
Please specify if Optional Interface or DC power is required.