National Instruments BNC-2090A User Manual

Also see for BNC-2090A: Quick start guide User manual

National Instruments BNC-2090A User Manual Manual pdf 29 page image

Chapter 3 Signal Conditioning© National Instruments Corporation 3-7 BNC-2090A User ManualFigure 3-4. Lowpass Filter on Differential Channel 1Figure 3-5 shows both the schematic and the component placement for a4 Hz lowpass filter placed on single-ended input channel 1. Refer to theInstalling Bias Resistors section for information about installing biasresistors.Figure 3-5. Lowpass Filter on Single-Ended Channel 1Building Highpass FiltersYou can install simple, RC highpass filters on any input channel of theBNC-2090A. The filters are useful for accurate high-frequencymeasurement and low-frequency noise rejection. By substituting resistanceand capacitance values into Equation 3-1, you can calculate a simple,one-pole RC filter to have a –3 dB cutoff frequency, fc. The frequencyresponse rolls off at a rate of –20 dB per decade decrease thereafter.Figure 3-6 shows a Bode plot of the amplitude versus normalizedfrequency.J10R29(C) = 19.8 kΩR26(D) = 19.8 kΩ+–C9(E) = 1 μFTo DAQDeviceAI 1J10R29(C) = 39.8 kΩAI 1R49(F)= 1 μFAI GNDAI 1AI GNDTo DAQDevice