Spider DSA User’s Manual
206
Strain Measurement and Analysis
Hardware
Spider-80SG
The Spider-80SG is an eight-channel strain/temperature sensor processing
system module useful for a wide range of physical tests and measurements.
Spider-80SG is a natural adjunct to Spider-80X systems for machinery
monitoring and modal analysis applications. This is a flexible module appropriate
for low frequency “static” stress/strain measurements and bearing temperature
monitoring as well as rapid dynamic stress analysis in vibration studies and
modal analysis. Though somewhat intricate to install, the tiny and nearly
massless strain gage is a marvelous sensor for vibration studies. It provides low-
frequency sensitivity unmatched by accelerometers and does so without mass
loading the object under study. Proper strain gauge installations can provide
much focused information, allowing you to separate tensile, bending and
torsional effects in a structure’s responses. Integrating these benefits within a
DSA system facilitates new levels of structural understanding.
The Spider-80SG module can be network-integrated or PC connected through its
Ethernet connector. It will precisely measure strain, based upon detecting small
changes in resistance when a wire or foil strain gage is stretched or compressed.
In similar fashion, it will accurately measure temperature from resistance changes
of a resistive temperature detector (RTD). It measures these with 24-bit digital
precision. Use it at sample rates up to 102.4 kHz to track dynamic strain
variations, or let it clock as slowly as o.48 Hz to trend near-DC temperature
trends.
Each input channel is a dedicated DC-excited Wheatstone Bridge circuit with 24-
bit digital output. Spider-80SG provides precision bridge-completion resistors for
use with either 120Ω or 350Ω gages. A precision calibration shunt resistor is also
provided, and shunt calibration is accomplished with a single command. The
software also provides facility for physical input calibration. The module will auto-
balance all channels upon command. There is no need to turn potentiometers or
switch resistors into the circuit; all module controls are through software.
Figure xx1: The Spider-80SG 8-channelstrain gage module
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