Overview

The National Instruments SCXI-1521 and SCXI-1521B are quarter-

bridge strain gage input modules that offer all of the features you need

for high-channel-count applications. Each NI SCXI-1521/B is shipped

with a NIST-traceable calibration certificate.

Each SCXI-1521/B module can multiplex its signals into a single

channel of the controlling DAQ device, and you can add more

modules to increase channel count.

Analog Input

Each of the 24 analog inputs of the SCXI-1521/B consists of a

quarter-bridge completion resistor (350

Ω for the SCXI-1521 and

120

Ω for the SCXI-1521B),and a 10 Hz,2-pole Butterworth filter.

You can program the excitation over 1024 different levels from 0 to

5 V. The 2-pole Butterworth filters provides lowpass filtering to block

noise and ensure measurement accuracy.

Calibration

The SCXI-1521/B modules provide simple yet powerful calibration

capabilities. Each module has an onboard calibration EEPROM that

stores calibration constants for each channel; factory calibration

constants are stored in a protected area of the EEPROM.

NI-DAQ traditional and NI-DAQmx transparently use the

calibration constants to correct for gain and offset errors for

each channel.

Null Compensation

Each input channel of an SCXI-1521/B includes a circuit to remove

bridge offset voltage. Driver software nulls the offset voltage to zero

in seconds. You do not need to manually adjust a potentiometer. By

removing this offset through the measurement hardware, you can

achieve better measurement resolution.

Shunt Calibration

Each input channel of an SCXI-1521/B includes an accurate and

stable shunt calibration resistor with which you can progamatically

simulate loading effects on your strain gage to compensate for

strain gage errors. The shunt calibration resistors located inside of

the module. You enable or disable the shunt resistors through

software commands.

Measurement Services Software

NI-DAQmx is the robust measurement services software included with all

National Instruments data acquisition and signal conditioning products.

This easy-to-use software tightly integrates the full functionality of your

DAQ hardware to LabVIEW, LabWindows/CVI, and Measurement Studio

for Visual Basic. High-performance features include multidevice

synchronization, networked measurements, and DMA data management.

Bundled with NI-DAQmx, the Measurement & Automation Explorer

(MAX) utility simplifies the configuration of your measurement hardware

with device test panels, interactive measurements, and scaled I/O channels.

NI-DAQmx also provides numerous example programs for LabVIEW

and other application development environments to get you started with

your application quickly.

SCXI Quarter-Bridge Strain Gage Input Module

Ω (SCXI-1521)

Ω (SCXI-1521B)

• Programmable excitation

(0 to 5 V) per channel

• Programmable shunt and null

calibration per channel

• 10 Hz filter per channel

• Onboard quarter-bridge completion

and shunt calibration resistors

• NI-DAQmx 7.3 simplifies

configuration and measurements

Operating Systems

• Windows 2000/NT/XP

Recommended Software

• LabVIEW

• LabWindows/CVI

• Measurement Studio

Other Compatible Software

• Visual Basic, C, C++

Measurement Services

Software (included)

• NI-DAQmx 7.3

Calibration Certificate Included

measurements, please consider the SCXI-1520.

NI SCXI-1521, NI SCXI-1521B

NEW

Terminal Block

Type

CJ Sensor

Compatible Modules

Cabling

Special Functions

Part Number

SCXI-1317

Screw terminals

–

SCXI-1521 & SCXI-1521B

–

–

777687-17

Front-mounting

Table 1. Terminal Block Options for the SCXI-1521/B