User manual

Chapter 3 Signal Conditioning

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 section for information about installing bias

resistors.

Figure 3-5. Lowpass Filter on Single-Ended Channel 1

Building Highpass Filters

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

. The frequency

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.

J10

R29(C) = 19.8 kΩ

R26(D) = 19.8 kΩ

–

C9(E) = 1 μF

To DAQ

Device

AI 1

J10

R29(C) = 39.8 kΩ

AI 1

R49(F)= 1 μF

AI GND

AI 1

AI GND

To DAQ

Device