ADLINK PXI-9527 - Manual (Page 33)

Operations 23
PXI-9527
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. DC coupling 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. AC coupling 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 3Hz.
Input for IEPE
For applications that require sensors such as accelerometers
or microphones, PXI-9527 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 PXI-9527 automatically sets input
configuration to AC coupling.
3.2.2 Input Range and Data Format
When using an A/D converter, properties of the signal to be mea-
sured should be considered prior to selecting channel and signal
connection to the module. Please refer to Section 2.5: Signal Con-
nection.
A/D acquisition is initiated by a trigger source, which must be pre-
determined. Data acquisition will commence once the trigger con-
dition is established. Following completion of A/D conversion, A/D
data is buffered in a Data FIFO, and can then be transferred to PC
memory for further processing.