Cronologic Ndigo5G-10, User Manual

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B
C2
C
D
T
G
C1
A
Figure 2.3: Schematics of an Ndigo5G board showing inter-board connectors C1 and C2.
2.2.2 Analog Inputs
TC1-1-I3M+
LemoD00 connector
analog-offset[i]
EV10AQ190
D
A
C
Figure 2.4: Input circuit for each of the four analog channels.
The analog inputs of the ADC are single ended LEMO00 coax connectors. The inputs have
a 50Ω impedance and are AC coupled. The inputs are converted to a differential signal using a
balun.
Analog Offsets
AC coupling removes the common mode voltage from the input signal. Users can move the
common mode voltage to a value of their choice using the analog offset parameter of each
channel before sampling.
This feature is useful for highly asymmetric signals, such as pulses from TOF spectrometers
or LIDAR systems. Without analog offset compensation, the pulses would begin in the middle
of the ADC range, effectively cutting the dynamic range in half (see Figure
2.6 ). By shifting
the DC baseline to one end of the ADC range, the input range can be used fully, providing the
maximum dynamic range. The analog offset can be set between
±
0 , 25 V .
cronologic GmbH & Co. KG 5 Ndigo5G User Guide