ADLINK PXIe-9529 - Manual (Page 24)

14 Operations
Differential and Pseudo-Differential Input Configuration
The PXIe-9529 provides both differential and psuedo-differen-
tial input configurations, with differential input mode providing
voltage to the anode and cathode inputs of the SMB connector
according to signal voltage difference therebetween. If the sig-
nal source is ground-referenced, differential input mode can be
used for common-mode noise rejection.
If the signal source is a floating signal, pseudo-differential input
mode can provide a reference ground connected to the cath-
ode input of the SMB through a 50 Ω resistor, preventing the
floating source from drifting over the input common-mode
range.
Recommended configurations for the signal sources are as fol-
lows.
AC and DC Input Coupling
AC and DC coupling are available. With DC coupling, DC offset
present in the input signal is passed to ADC, and is indicated if
the signal source has a small level of offset voltage or if DC
content of the signal is important. In AC coupling, the DC offset
present in the input signal is erased, and is indicated if the DC
content of the input signals is to be rejected. AC coupling
enables a high pass R-C filter through the input signal path.
The corner frequency (-3dB) is about 0.5Hz.
Input for IEPE
For applications that require sensors such as accelerometers
or microphones, the PXIe-9529 provides an excitation current
source. The common excitation current is usually about 4mA
for these IEPE sensors. A DC voltage offset is generated due
to the excitation current and sensor impedance. When IEPE
current sources are enabled, the PXIe-9529 automatically sets
input configuration to AC coupling.
Signal Source Type Card Configuration
Floating Pseudo Differential
Ground-Reference Differential