Chapter 2
Configuration and Installation
© National Instruments Corporation
2-7
SCXI-1100 User Manual
acquisition boards, such as the Lab boards and the PC-LPM-16, place jumper W10 in position
AB-R0 to connect the data acquisition board ground reference to the module analog ground
reference.
Reference Mode Selection
Jumper W1
Jumper W1 references the negative (-) input of the PGIA to ground through a 100 k
Ω
resistor.
The SCXI-1100 is shipped with jumper W1 in the parking position. Use this setting when
connecting to signals that are referenced to ground.
If you are measuring floating sources, you can move jumper W1 to position 3 to reference the
negative (-) input of the PGIA to ground through the 100 k
Ω
resistor. Refer to Figures 2-3, 2-4,
and 2-5 later in this chapter for signal connection diagrams.
Note:
If all of the sources are floating, you can configure jumper W1 to connect a 100 k
Ω
resistor to the negative input of the amplifier to prevent saturation of the amplifier
inputs. This reduces the input impedance, however, and usually increases settling time
and common-mode noise. Also, if any of the sources are ground-referenced or have
high leakage to ground, a ground loop can result, causing DC offsets or noise.
Therefore, it is best if you do not use this jumper but instead connect your floating
channels to the chassis ground on the terminal block via a wire.
Table 2-3. Jumper W1 Settings
Jumper
Description
Configuration
W1
Factory setting; parking position (used
for ground-referenced sources)
•
•
•
1 2 3
W1
Floating source connection
•
•
•
1 2 3
For more information on input signal connections, see the Signal Connections section later in this
chapter.
Filter Selection
Jumpers W2 through W4
One jumper block is provided for jumpers W2, W3, and W4:
•
When you connect jumper W2, the SCXI-1100 does not filter.
•
When you connect jumper W3, a 10 kHz lowpass filter filters the conditioned signal.
•
When you connect jumper W4, a 4 Hz lowpass filter filters the conditioned signal.
