National Instruments BNC-208 Series, User Manual

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BNC-2080 Board Chapter 2
BNC-208X Series User Manual 2-14 © National Instruments Corporation
Channel 9
(-in) Channel 1
(+in)
BNC Connector
R4
R11
R15
R21
R3
R20
C2
100-k
1
Resistor
Channel 9
(-in {Case})
Channel 1
(+in {Center})
F
G
(C2)
D
E
AIGND
To
Input
Multiplexer
Input Schematic for
ACH1
BNC Connector
R15 = 100 k
1
+
-
R3
R20
A
B
C
D
E
F
G
Figure 2-11. Bias Return Resistor for DC-Coupled Floating Source on Channel 1 in
DIFF Mode
Single-Ended Inputs
When measuring floating signal sources, the MIO-16 board should be configured to supply a
ground reference. Therefore, the MIO-16 should be configured for RSE mode. In this
configuration, the negative input of the MIO-16 instrumentation amplifier is tied to the analog
ground. Therefore, the BNC-2080 board should be used in its factory configuration. In the
factory configuration, jumpers are in the two series positions,
E
and
F
(see Table 2-2). In this
configuration, all of the signal grounds should be tied to AIGND. Signal conditioning circuitry
such as filters and attenuators, as described in the sections titled
Building Lowpass Filters ,
Building Highpass Filters ,
and
Building Attenuators (Voltage Dividers)
later in this chapter, can be
built in the open component positions.