National Instruments BNC-208 Series, Руководство пользователя

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Chapter 2 BNC-2080 Board
© National Instruments Corporation 2-9 BNC-208X Series User Manual
Mounting
The BNC-2080 board is equipped with metal standoffs so the board can be placed on a workbench
near the host computer. You can use an optional rack-mount chassis, which can be fitted with a
flat, acrylic plastic cover. When the BNC-2080 board is mounted in the chassis, the board can be
grounded to its metal standoffs, and therefore to the rack. For more information, see Chapter 4,
Installation and Connections
.
Application Notes
The open component positions on the BNC-2080 board make adding signal conditioning
components to the analog input signals easier. Several applications are covered in this section,
including filtering and attenuation.
The figures in this section give examples on a specific input channel. If you want to install the
circuit on a different channel, consult Table 2-3 to determine the equivalent component positions
for the other channels.
Soldering and Desoldering on the BNC-2080 Board
The applications discussed here require you to make modifications to the printed circuit board,
usually by removing jumpers and adding components. The BNC-2080 board is shipped with wire
jumpers in the
E
and
F
positions (see Table 2-3 and Figure 2-3). Use a low-wattage soldering iron
(20 to 30 W) when soldering to the board. To desolder on the BNC-2080, vacuum-type tools
work best. Use care when desoldering to avoid damaging component pads. Only rosin-core,
electronic-grade solder should be used. Acid-core solder damages the printed circuit board and
components.
Channel Configurations
MIO-16 Analog Input
This section discusses the input configuration of the MIO-16 board and the corresponding
configurations of the BNC-2080.
The analog input channels of an MIO-16 data acquisition board can be configured for one of three
input modes: differential (DIFF) input mode, referenced single-ended (RSE) input mode, or
nonreferenced single-ended (NRSE) input mode.
Although the open component positions are placed to facilitate use with differential inputs, any of
the three modes can be selected. If the MIO-16 board is configured in the RSE mode, all 16 analog
input channels are referenced to AIGND. If the MIO-16 board is configured in the NRSE mode,
resistors should not be inserted into positions
B
or
D
of Figure 2-3 for any channel. Doing so can
cause inaccurate readings because of incorrect ground reference. Resistors can be inserted into
these positions in the RSE mode. For information on the input configurations, see your MIO-16
board user manual.
The BNC-2080 board can be configured to work with all three MIO-16 input configurations. The
DIFF mode is configured by flipping the switches next to each pair of BNC connectors to DIFF.
This must be done to
all
eight switches in order to have eight differential channels. In DIFF mode,
the first eight analog (ACH0 through ACH7) BNC connectors are used. The remaining eight