ETC_1960 pages

SCXI Isolated Universal Input

SCXI Isolated Universal Input Modules
NI SCXI-1121, NI SCXI-1122
• Isolated analog inputs
• Isolated voltage and
current excitation
• Signal inputs from millivolts
to ±250 V
• Lowpass filtering
• Shunt calibration
• NI-DAQ driver software simplifies
configuration, measurements,
and scaling

SCXI-1121
• 4 isolated input channels
• 4 isolated excitation channels
• 250 Vrms working isolation
per channel
• Offset nulling and shunt calibration
with SCXI-1321

SCXI-1122
• 16 channels
• 100 S/s (4 kHz filter), 1 S/s
(4 Hz filter)
• 2 excitation sources
• 480 Vrms working isolation
per channel

Operating Systems
• Windows 2000/NT/XP

Recommended Software
• LabVIEW
• LabWindows/CVI
• Measurement Studio
• VI Logger

Driver Software
• NI-DAQ 7

Data Acquisition and
Signal Conditioning

Overview
The National Instruments SCXI-1121 and SCXI-1122 modules are
designed for a wide variety of sensor and signal inputs requiring
isolation. The NI SCXI-1121 offers independent jumper-configurable
isolation amplifiers, filters, and excitation sources for each channel.
The SCXI-1122 offers an isolation amplifier, filter, and excitation source
for all channels. Both SCXI-1121 and SCXI-1122 modules offer at
least 250 Vrms working isolation and can acquire strain, RTD,
thermocouple, millivolt, volt, 250 V, 0 to 20 mA, and 4 to 20 mA
current input signals. Both modules can multiplex their channels
into a single channel of the controlling DAQ device. The SCXI-1121
also offers parallel-mode operation. If you are specifically interested
in strain measurements, consider using the NI SCXI-1520 Universal
Strain Gauge Input Module. For thermocouple measurements,
consider using the NI SCXI-1102 Thermocouple Input Module.
For RTD measurements, consider using the SCXI-1102 in combination
with the SCXI-1581 Current Excitation Module or the PXI-4070
DMM with SCXI-1127 switch.

Analog Input
SCXI-1121
The analog inputs of the SCXI-1121 consist of four isolated
instrumentation amplifiers. You can configure each channel
independently using jumpers for input ranges of ±2.5 mV to ±5 V.
You can extend the input range for each channel to ±250 VDC/
±250 VAC with the SCXI-1327 terminal block. Each channel also
includes a lowpass filter that you can configure using jumpers for 4 Hz or
10 kHz. You can sample channels at a rate up to 333 kS/s (3 µs per
channel in multiplexed mode). Each channel offers transducer-specific
features such as bridge completion, configurable voltage and current

300

excitation, bridge balancing, and shunt calibration depending on the
configured terminal block. Each channel is individually isolated with
a working voltage limit of 250 Vrms between channels or channel to
earth. Finally, the SCXI-1121 is CE certified as double insulated,
Category II, for 250 Vrms of operational isolation.

SCXI-1122
The SCXI-1122 consists of 16 relay multiplexers that route the input
channels to a single isolated instrumentation amplifier and lowpass
filter. You can program all inputs together for a range of ±5 mV to
±250 V. You can program the lowpass filter setting for all input
channels for either 4 Hz or 4 kHz. With this relay multiplexer
architecture, you are limited to a maximum sampling rate of 100 S/s
for the 4 kHz filter setting, and 1 S/s for the 4 Hz filter setting on all
channels in your scan list. Thus, the SCXI-1122 is not intended to be
used for the scanning of multiple channels. It should be used to acquire
multiple samples from a single channel before acquiring from the next
channel. This module also offers cold-junction compensation, bridge
completion, and a single voltage and current excitation source with
remote sensing. You can configure the SCXI-1122 for 4-wire scanning
mode, accepting up to eight 5 k devices. You can also connect up to
16 devices in series. Each channel is individually isolated with a working
common-mode voltage of 250 Vrms between channels or 480 Vrms
channel to earth. Finally, the SCXI-1122 is CE certified as double
insulated, Category II, for 250 Vrms of operational isolation.

SCXI Module
SCXI-1121
SCXI-1122

Bridge
✓
✓

Table 1. Signal Compatibility

National Instruments • Tel: (800) 433-3488 • Fax: (512) 683-9300 • info@ni.com • ni.com

RTD
✓
✓

Thermocouple
✓