User manual

Chapter 3 Signal Conditioning

Note Highpass filters generally exhibit poorer common-mode rejection characteristics

than lowpass filters because capacitors are in the series input paths. Capacitors have poorer

tolerances than resistors, and matching the input impedances is crucial for good

common-mode rejection.

Figure 3-7 shows both the schematic and the component placement for a

50 kHz highpass filter placed on differential input channel 1. If the input

signal source is floating, you must place a bias return resistor in positions

A and/or B position (R28 and R27, respectively). Refer to the Installing

Bias Resistors section for information about installing bias resistors.

Figure 3-7. Highpass Filter on Differential Channel 1

Figure 3-8 shows both the schematic and the component placement for a

50 kHz highpass filter placed on single-ended input channel 1. Refer to the

Installing Bias Resistors section for information about installing bias

resistors.

Figure 3-8. Highpass Filter on Single-Ended Channel 1

R29(C) = .001 μF

R26(D) = .001 μF

–

C9(E) = 6.34 kΩ

To DAQ

Device

J10

AI 1

R29(C) = .0005

μF

R49(F) = 6.34 kΩ

J10

AI 1

AI GND

To DAQ

Device