SFR Top Image 

Theoretical Amplitude Response

Filter Description Type Comments
Anti aliasing 01

Flat to cut off, sharp filter for anti-aliasing and similar applications.

136 dB/Octave equivalent slope, -80dB stop band. > - 79 dB at 2 Fc

General purpose 41

Flat to cut off, linear phase, good general purpose filter

52 dB/Octave equivalent slope, -82dB stop band.  - 31 dB at 2 Fc  

8 pole Butterworth 03

Classic 8 pole 48dB/Octave Butterworth filter, -3dB at cut off

48 dB/Octave equivalent slope, monotonic stop band.  - 48 dB at 2 Fc 

4 pole Butterworth 05

Classic 4 pole 24dB/Octave Butterworth filter, -3dB at cut off

24 dB/Octave equivalent slope, monotonic stop band.  - 24 dB at 2 Fc

8 pole Bessel 07

Classic 8 pole 48dB/Octave Bessel filter, -3dB at cut off

48 dB/Octave equivalent slope, monotonic stop band.  - 24 dB at 2 Fc

4 pole Bessel 09

Classic 4 pole 24dB/Octave Bessel filter, -3dB at cut off

24 dB/Octave equivalent slope, monotonic stop band.  - 13 dB at 2 Fc

 

FilterResponse TimeResponsetoStepInput 

Time Response to Step Input

FilterResponse NormalizedFreq Graph

Passband Phase Response

The curves above show the theoretical phase response of the standard filter responses 

 

FilterResponse PhaseDeviation

 

Passband Phase Deviation

The curves above show the theoretical passband phase variation for the standard filter responses.

Standard Filter Responses

Anti-Aliasing (01) – a filter optimised for anti-aliasing protection before sampling and A-D conversion, where analysis is in the frequency domain.

General Purpose (41) – a filter optimised for low signal distortion. Flat passband and linear phase characteristics, with moderate settling time.

Butterworth (03, 05) – traditional Butterworth filters, often used to match existing systems, type 01 is superior for alias protection, and type 41 is a better general purpose filter. Bessel (07, 09) – traditional Bessel filters, linear phase, and low time delay with minimal overshoot, but with significant roll off in the passband.

General Notes about Filter Responses

Selecting a filter for a signal conditioning application can be difficult. However many filtering applications are similar and can be solved using a few optimised filter responses.
All filters, whether analogue or digital, change the signals passing through them. For any filter characteristic, the filter effect is strongly dependant on the kind of information contained in the signal. 

We have a page that may be of interest that looks at the best filter for your Task. 

Kemo has been manufacturing filtering systems for over 50 years. The many applications to which our filters have been put have resulted in a wide range of filter responses. Our Standard Response  data sheet shows a range of filter responses which covers most needs, many of these are held in stock. 

We feel that it is important to be able to compare the technical performance of different types of filter in a consistent way. Our "Filter Response Information Leaflets" use a uniform format to provide a complete picture of the filter characteristics in the amplitude, phase and time domains, independent of the intended application. This is of course no substitute for experimentation, and we encourage users to explore the performance of their system with filters fitted, to get an idea of not only of the suitability of the response itself, but also the signal quality aspects of the hardware (noise, linearity, offset etc) which are also related to the choice of the option response. 

There are leaflets for the most used Kemo filter responses, each with a brief description of the type of filter.

 

Standard Filter Responses

Anti-aliasing Filter Response: 01LP
Filter order and type: n=8 lowpass Basic stopband: -80dB at 1.5 times Fc

8 Pole Butterworth Filter Response: 03LP
Filter order and type: n=8 lowpass Basic stopband: 48dB/octave (48dB at 2 times Fc)

4 PoleButterworth Filter Response: 05LP
Filter order and type: n=4 lowpass Basic stopband: 24dB/octave (24dB at 2 times Fc)

8 Pole Bessel Filter Response: 07LP
Filter order and type: n=8 lowpass Basic stopband: 48dB/octave (-13dB at 2 times Fc)

4 Pole Bessel Filter Response: 09LP
Filter order and type: n=4 lowpass Basic stopband: 24dB/octave (-13dB at 2 times Fc)

General Purpose Filter Response: 41LP
Filter order and type: n=8 lowpass Basic stopband: -82dB at 3 times Fc Linear Phase

 

BenchMaster 8 Filter Responses

Filter Set: 8.03 Butterworth, Flat and Pulse 
Filter order and type: n=8 lowpass Basic stopband: 48dB/octave (-52dB at 2 times Fc)
Filter set for BenchMaster 8.03.

Filter Set:8.05 Butterworth, Flat, and Pulse 
Filter order and type: n=4 lowpass Basic stopband: 24dB/octave (-26dB at 2 times Fc)
Filter set for BenchMaster 8.05.

Filter Set: 8.13 Butterworth, Flat, and Pulse  
This Response is available as Option 13 on Benchmaster 21M
Filter order and type: n=8 lowpass Basic stopband: -93dB at 2 times Fc
Filter set for BenchMaster 8.13.

 

Some Additional Filter Responses

Notch Filter Sharp Q=10
Filter order and type: n=8 notch, stopband >-80dB
Optimized for 50 Hz and 60 Hz.
Available as 1200 Series Filter Modules or Din Rail Only

Filter Response: L1 Standard on VBF40 & 44 Only
Filter order and type: n=8 lowpass Basic stopband: -80dB at 1.5 times Fc

Filter Response: L2 Standard on VBF40 & 44 Only
Filter order and type: n=8 lowpass Basic stopband: -116dB at 4.6 times Fc
Filter set for VBF40 Series

Filter Response: 21LP Special Order
Filter order and type: n=6 lowpass Basic stopband: -102dB at 4 times Fc

Filter Response: 21pulLP Special Order
Filter order and type: n=6 lowpass Basic stopband: -102dB at 4 times Fc

Filter Response: 31LP Special Order
Filter order and type: n=6 lowpass Basic stopband: 36dB/octave (36dB at 2 times Fc)

Filter Response: 31pulLP Special Order
Filter order and type: n=6 lowpass Basic stopband: 36dB/octave (-39.3dB at 2 times Fc)

Filter Response: 37LP Benchmaster 21M
Filter order and type: n=6 lowpass Basic stopband: -82dB at 3 times Fc

Filter Response: 37pulLP Benchmaster 21M
Filter order and type: n=6 lowpass Basic stopband: -82.9dB at 3 times Fc

Filter Response: 79LP Special Order
Filter order and type: n=6 lowpass Basic stopband: -70dB at 3 times Fc

Filter Response: 85LP Special Order
Filter order and type: n=8 lowpass Basic stopband: -78dB at 2 times Fc

In addition to the filter responses listed above we have many more filter designs that can be made available if your needs are not met one of those shown.