Building Highpass Filters - National Instruments BNC-2090A User Manual

Building Highpass Filters

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To DAQ
Device
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Figure 3-4. Lowpass Filter on Differential Channel 1
Figure 3-5 shows both the schematic and the component placement for a
4 Hz lowpass filter placed on single-ended input channel 1. Refer to the
Installing Bias Resistors
resistors.
AI 1
R49(F)= 1 μF
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Device
Figure 3-5. Lowpass Filter on Single-Ended Channel 1
You can install simple, RC highpass filters on any input channel of the
BNC-2090A. The filters are useful for accurate high-frequency
measurement and low-frequency noise rejection. By substituting resistance
and capacitance values into Equation 3-1, you can calculate a simple,
one-pole RC filter to have a –3 dB cutoff frequency, f
response rolls off at a rate of –20 dB per decade decrease thereafter.
Figure 3-6 shows a Bode plot of the amplitude versus normalized
frequency.
R29(C) = 19.8 kΩ
C9(E) = 1 μF
R26(D) = 19.8 kΩ
section for information about installing bias
R29(C) = 39.8 kΩ
AI GND
AI GND
3-7
Chapter 3 Signal Conditioning
AI 1
J10
AI 1
J10
. The frequency
c
BNC-2090A User Manual