Chapter 2 Configuration, Installation, and Signal Connection
BNC-2090 User Manual
2-2
National Instruments Corporation
Mode Configuration
The BNC-2090 is factory-configured for use with the MIO board in the
DIFF mode. Therefore, you must configure the BNC-2090 if you want
to use the accessory with the MIO board in either RSE or NRSE mode.
The BNC-2090 has nine front panel switches, shown in Figure 2-1, that
configure the accessory for differential (DIFF), referenced single-ended
(RSE), or nonreferenced single-ended (NRSE) mode.
If you want to measure floating signal sources, configure the MIO board
for DIFF or NRSE mode, both of which require bias resistors, or for
RSE mode. Refer to Chapter 3,
Signal Conditioning Application
Examples
, for information on installing bias resistors.
If you want to measure ground-referenced signal sources, configure the
MIO board for the NRSE mode or DIFF mode. Both types of signal
sources are discussed in the following sections.
If you configure the MIO board in the RSE mode, all 16 analog input
channels are referenced to AIGND. For more information on the input
configurations, see your MIO board user manual.
DIFF Input Mode
The BNC-2090 is factory-configured for DIFF mode so that all eight
switches (SW1–SW8) are in the DIFF position. In DIFF mode, the first
eight analog BNC connectors (ACH<0..7>) are used and the remaining
eight analog BNC connectors (ACH<8..15>) are not used. (BNC-2090
switch SW9 position is irrelevant in this mode.) Make sure that your
MIO board is configured for DIFF input mode.
Note:
All of the switches are required to be in the same position; that is, S1
through S8 must all be in either the DIFF position or in the SE position.
RSE and NRSE Input Mode
First, configure the MIO board for RSE or NRSE input mode. Next,
configure the BNC-2090 for SE mode by flipping all eight switches
(SW1–SW8) next to each pair of BNC connectors to SE to have 16
single-ended channels. In this mode, all 16 BNC connectors are in use
and all 16 BNC shields are tied to a common signal. You can switch the
common signal between AIGND and AISENSE through switch SW9.
AISENSE is tied to a common signal for NRSE mode configuration and
AIGND is tied to a common signal for RSE mode configuration.
