Chapter 3
Configuring Your SCXI Hardware and Software
©
National Instruments Corporation
3-15
The SCXI-1121 is factory-configured for use with an MIO or AI device
in DIFF mode. Each module channel is configured for a gain of 1,000
(an input range of ±5 mV), 4 Hz filtering, 3.33 V voltage excitation,
and disabled bridge completion. If this configuration is suitable for your
application, do not reposition any of the jumpers. However, you must adjust
the jumper configuration if any of the following conditions is true:
•
You are cabling the SCXI-1121 module 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.
•
You need a different gain or bandwidth (other than 1,000 and 4 Hz)
on any channel.
•
Your transducers require current excitation or 10.0 V voltage
excitation.
•
Your transducers require half-bridge completion circuitry.
•
You are using digital modules and are cabling the SCXI-1121 to
a DAQ device.
Read the rest of this section on the SCXI-1121 module if any of the
previous conditions applies to you.
Use the following procedure to configure your SCXI-1121 module:
1.
Configure the gain.
You select the gain for each SCXI-1121 channel in two stages, each of
which is jumper controlled. The default gain for each channel is 1,000.
The total gain produced on a particular channel is equal to the product
of the first-stage and second-stage gains applied to that channel, as
shown by the following equation:
Total gain (channel n) = first-stage gain (channel n) • second-stage
gain (channel n)
The effective input range that you can measure with a particular
gain is:
a.
Configure the first-stage gain selection.
Use jumpers W3, W19, W29, and W41 to configure the first-stage
gain of channels 0 through 3, respectively. Each jumper has four
possible positions—A, B, C, and D—each corresponding to a
particular gain.
Input range V
( )
±5V
total gain
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