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The BenchMaster 8 series of variable filters are now in their
5th 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.
Summary Specification
| Channels |
2 per
unit (independent) |
| Control |
All
functions by front panel switches.
External control option, 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
Elliptic13. |
| Filter Bypass |
Yes |
| Filter Modifiers |
Flat, Butterworth, Pulse ( not all
operate with all filter responses) |
| Signal Invert |
Yes |
| 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 |
| Size |
1U 19" |
| 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.
Flexible Input
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.
Input Gain
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. This 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 in if
required the two channels can 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, Flat, and Pulse.
'pulse' modifier, a minimum overshoot response, the normal operating position
for the Bessel response 8.07 and 8.09.
'flat' modifier, with a flattened amplitude response up to the cut-off
frequency, the normal operating position for responses 8.13 and 8.41.
'but' modifier, provides a -3dB at cut off type response, the normal operating
position for the Butterworth response 8.03 and 8.05.
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
FICL
II
interface for external computer control. This is a text (ASCII) over a
10BaseT, RJ45 plug, Ethernet style hardware interface. This provides an
operating system independent interface. The interface stores current
data, verifies incoming commands, and then executes them.
Simple text commands are used, the screen image shows typical commands
sent via HyperTerminal.
freq,1,250 - sets channel 1, frequency to value 250
icpl,1,dc - sets channel 1, input coupling to
DC.
fran,1,L2 - sets channel 1 to range L(lowpass) 2
(102)
igna,2,5 - sets channel 1, input gain
block A to x5.
rdbk,2 reads back
all the current settings for channel 1.
The RDBK (readback) command gives a listing of all the commands.
RDBK,A will readback all the settings for both channels.
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. |
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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 8.07 - 4 Pole Bessel response NOTE the
filter modifiers Flat and Butterworth are not available with this response
BenchMaster 8.09 - 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
DC Power (optional)
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.
Other Features
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.
Ordering Information
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
DC power is required.
BenchMaster 8 pdf data sheet (75 kB)
Order Form
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