17-2000 C
2020-09-17
9(50)
ADQ8-8C Manual
17-2000 C 2020-09-17
9(50)
2
SETTING UP THE ANALOG FRONT-END
2.1 ADQ8-8C AFE block diagram
The analog front-end setup for ADQ8-8C found in
.
2.2 Set input impedance
The analog input impedance can be set on the PXIe version to 50
or 1 M
. The control is individual
per channel. The available analog signal ranges are the same for both impedance settings.
The MTCA.4 version of ADQ8-8C–VG is always 50
terminated to ground.
2.3 Set analog input range
On ADQ8-8C–VG, the input range is variable. The requested input signal range is sent to the API,
which reads available settings and return the best selection. The actual value of each range is available
for calculations according to the following:
DESIRED_ANALOG_RANGE
is the requested range set
into
SetInputRange
.
#
DESCRIPTION
USER COMMAND
REF
a
PXIe form factor: The analog input impedance can be set to 50
or 1 M
MTCA.4 form factor: input is impedance is fixed 50
to GND
SetInputImpedance
b
On ADQ8-8C-VG, the gain can be set in a discrete number of steps. By
requesting a certain range, the closest available setting is activated. The
actual range that is set is returned to the user. Note that the compensation
has to be done in the software.
Changing the input range requires a settling time of 1 s.
SetInputRange
c
Set a DC offset for better using the signal range when the signal is
unipolar.
Changing the DC offset requires a settling time of 1 s.
SetAdjustableBias
d
The gain and offset is calibrated using a 32 MHz -1dBFS sine wave
signal. The digital compensation corrects the offset and the gain at this
frequency.
The user can access this block to set a different gain and offset. Note that
this is a digital gain and offset adjustment and not the same as selecting
analog input range in the –VG option.
SetGainAndOffset
Figure 3:
AFE control.
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