Chapter 3
Configuring Your SCXI Hardware and Software
3-4
www.ni.com
SCXI-1100 Module
This module is a 32-channel differential-input multiplexer with an onboard
programmable-gain instrumentation amplifier (PGIA). The SCXI-1100 has
32 differential voltage or current input channels, an analog input range of
±10 V, jumper-selectable lowpass filters of 4 Hz and 10 kHz, and
software-selectable module gains of 1, 2, 5, 10, 20, 50, 100, 200, 500,
1,000, and 2,000. The SCXI-1100 works only in multiplexed mode and
drives two analog input channels on the DAQ device—channel 0 and
channel 1.
The SCXI-1100 is factory-configured for use with an MIO or AI device in
DIFF mode, using ground-referenced signals, with no filtering. If this
configuration is suitable, do not reposition any jumpers. However, you must
adjust the configuration if any of the following conditions is true:
•
You are cabling this SCXI-1100 directly to a DAQ device and you are
using a Lab or 1200 device, or you are using an AI or MIO device in
SE mode.
•
Your input signals are floating or nonreferenced and you want to
ground reference the signals through a 100 k
Ω
resistor installed in the
module; however, it is best to ground-reference the signals at the
source or at the terminal block.
•
You need hardware filtering and can accept slower scan rates.
•
You are measuring current signals.
Read the rest of this section on the SCXI-1100 module if any of the
previous conditions applies to you.
The SCXI-1100 module has five user-configurable jumpers for configuring
input signal referencing, filtering, and PGIA output referencing. Leave all
other jumpers in their factory-default positions.
Use the following procedure to configure your SCXI-1100 module:
1.
Configure the input signal referencing mode.
For ground-referenced sources, leave jumper W1 in the factory-default
position. This is the preferred position.
Caution
If you plan to use any floating thermocouples or other floating-source
transducers, National Instruments recommends that you leave jumper W1 in the
factory-default setting and either ground the negative lead of each transducer to the chassis
ground on your terminal block, or reference the transducer to ground at the source. In either
case, the transducer must not have a high common-mode voltage. Ground your signal at