ADLINK Technology MCM-100, User Manual

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36 Operation
Leading
EDGE COMPUTING
Input Coupling
When DC coupling is selected, DC offset present in the input sig-
nal is passed to ADC. DC coupling configuration is indicated when
the signal source has a small offset voltage or if the DC content of
the signal is important. When AC coupling is selected, DC offset
present in the input signal is removed. AC coupling configuration
is indicated when 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, with corner frequency (-3dB) about 0.4 Hz.
IEPE Input
For applications utilizing sensors such as accelerometers or
microphones, the MCM-100/102 provides an excitation current
source.
The excitation current is 2 mA for the IEPE sensors, with DC volt-
age offset generated because of the excitation current and sensor
impedance. When enabling IEPE current sources, the MCM-100/
102 automatically sets input configuration to AC coupling.
Figure 4-2: Excitation Current for IEPE Sensor Measurement
2mA
Constant
Current
VCC
IEPE ON/
OFF
AI Channel
IEPE Sensor
MCM-100
Analog Front End