Measurement Computing WaveBook rev.3.0 - Manual (Page 59)

WaveBook User’s Manual, ch03B 6-23-99 WBK Expansion Options, WBK16 3-27
Low-Pass Filter Customization
WBK16 has 68 k
Ω 4-resistor SIP networks installed from the factory. These networks result in a 10.9 Hz
cutoff for filter A and a 1.09 kHz cutoff for filter B. The 4-resistor SIP networks are socketed and can be
altered to the range of values in the table below. Individual resistors may also be used but should be
matched within 2%. Cutoff frequency accuracy is about ±5%.
If you change the filter nominal values, be sure to update the filter cutoff frequencies in
the WaveView software. This is discussed in the section, WaveBook Advanced Features,
on page 3-43.
Resistor Filter A Resistor Filter B
330 k Ω 2.20 Hz 330 k Ω 225 Hz
450 k Ω 4.95 Hz 450 k Ω 495 Hz
120 k Ω 3.37 Hz 120 k Ω 337 Hz
100 k Ω 7.42 Hz 100 k Ω 742 Hz
82 k Ω 9.05 Hz 82 k Ω 905 Hz
68 k Ω 10.9 Hz 68 k Ω 1.09 kHz
47 k Ω 15.8 Hz 47 k Ω 1.57 kHz
33 k Ω 22.5 Hz 33 k Ω 2.25 kHz
22 k Ω 33.7 Hz 22 k Ω 3.37 kHz
15 k Ω 49.5 Hz 15 k Ω 4.95 kHz
10 k Ω 74.2 Hz 10 k Ω 7.42 kHz
8.2 k Ω 90.5 Hz 8.2 k Ω 9.05 kHz
6.8 k Ω 109 Hz 6.8 k Ω 10.9 kHz
4.7 k Ω 158 Hz 4.7 k Ω 15.8 kHz
3.3 k Ω 225 Hz 3.3 k Ω 22.5 kHz
3 to 330 k Ω R=742K/f
cut
3 to 330 k Ω R=74.2M/f
cut
Lower frequency filters, such as the 10-Hz filter provided, are generally used to reduce higher frequency
noise. Some common sources of noise are: 50/60 Hz power line pickup on long cables, electromagnetic
interference (EMI) from nearby equipment, unwanted vibrations in the strain gage system itself, or at higher
gains, the intrinsic thermal noise of the amplifiers. All information above the cutoff will also be lost due to
the filter’s function.
The 1-kHz filter provided is typically used as an anti-aliasing filter, or for slight noise reduction while still
maintaining moderate bandwidth.
Reference Note:
The next several pages contain schematics of various bridge configurations. Page 3-32
contains DB9 connector information, including use of the optional CN-189, DB9 Adapter.