
Chapter 2 Configuration, Installation, and Signal Connection
BNC-2090 User Manual
2-12
National Instruments Corporation
SE Inputs
When measuring floating signal sources, configure the MIO board to
supply a ground reference by placing the board in RSE mode. This
mode ties the negative input of the MIO board instrumentation
amplifier to the analog ground.
When the MIO board is configured for RSE mode, keep your
BNC-2090 in the factory-default configuration, in which the 0
Ω
jumpers are in the two series positions, C and D (see Table 3-1) and all
of the signal grounds are tied to AIGND. Refer to Chapter 3,
Signal
Conditioning Application Examples
,
for information on building
additional signal-conditioning circuitry, such as filters and attenuators,
in the open-component positions.
Connecting Ground-Referenced Signal Sources
A grounded signal source is connected in some way to the building
system ground; therefore, the signal source is already connected to a
common ground point with respect to the DAQ board (assuming the
host computer is plugged into the same power system). The nonisolated
outputs of instruments and devices that plug into the building power
system fall into this category.
DIFF Inputs
If the MIO board is configured for differential inputs, ground-
referenced signal sources connected to the BNC-2090 need no special
components added to the BNC-2090. You can leave the inputs of the
BNC-2090 in the factory-default configuration, with the 0
Ω
jumpers in
the two series positions, C and D (see Table 3-1). Refer to Chapter 3,
Signal Conditioning Application Examples,
for information on building
signal-conditioning circuitry, such as filters and attenuators, in the
open-component positions.
SE Inputs
When measuring ground-referenced signals, the external signal
supplies its own reference ground point and the MIO board should not
supply one. Therefore, configure the MIO board for the NRSE mode, in
which all of the signal grounds are tied to AISENSE, which connects to
the negative input of the instrumentation amplifier on the MIO board.
You can leave the inputs of the BNC-2090 in the factory-default
configuration, with the 0
Ω
jumpers in the series position (C or D,
depending on the channel). You should not use the open positions,