Developing a Strain Measurement Solution Using NI LabVIEW Software and Data Acquisition
Hardware
"According to the new testing procedure, each
channel’s sampling rate must be more than 20 kS/s,
which is difficult to achieve. We met this challenge
using the NI SCXI-1520 universal bridge input
module and NI SCXI-1000 4-slot chassis."
- Alan Ho, Chief-SI (http://partners.ni.com/partner_locator/partner_details.aspx?id=92264)
The Challenge:
Developing a high-speed strain gage measurement system for testing computer printed circuit boards (PCBs), motherboards, and mobile phones.
The Solution:
Using LabVIEW software combined with NI SCXI or NI CompactDAQ hardware to design a complete strain measurement solution suited for testing
microstrain gaging and temperature distortion.
Author(s):
Alan Ho - Chief-SI (http://partners.ni.com/partner_locator/partner_details.aspx?id=92264)
Strain is a required measurement for a range of applications from structural tests to bridge and dam health monitoring to PCB stress distortion
measurements. Even though strain is a fundamental measurement, many people are still not familiar with the various aspects such as performing strain
tests and high temperature distortion gauging on PCB motherboards.
To help address PCB strain gage measurement, we developed a turnkey solution called StrainMap using LabVIEW (
http://www.ni.com/labview/?metc=mt5mq3) software and NI modular hardware such as SCXI and NI CompactDAQ (
http://www.ni.com/data-acquisition/compactdaq/). StrainMap, a suitable solution for most strain measurements, is most commonly used for measuring the
strain on PCB motherboards and the strain and acceleration for mobile phone drop tests.
Strain Measurement Challenges
To make a strain measurement, we have to choose a suitable strain gage based on the testing purpose and environment. Strain gage installation also has
specific steps and procedures.
At least 12 strain measurement channels are required for strain testing on motherboard PCBs, and common applications require at least 24 synchronized
channels with three additional sets of acceleration channels for mobile phone drop testing. Also, according to the new testing procedure, each channel’s
sampling rate must be more than 20 kS/s, which is difficult to achieve. We overcame this challenge using the NI SCXI-1520 (
http://sine.ni.com/nips/cds/view/p/lang/en/nid/202267?metc=mtcptj) universal bridge input module and NI SCXI-1000 4-slot chassis.
Considering data, users are most interested in the maximum strain value over the period of the test rather than individual strain values. Software based on
LabVIEW in the StrainMap solution provides a user-friendly GUI, configuration wizards, Mohr’s circle analysis, and strain-rate calculation.
Strain measurement equipment generally includes a strain gage sensor; signal terminal connectivity; a module with bridge completion, excitation, and
filtering for signal conditioning; a chassis; and a 16-bit data acquisition device for analog-to-digital conversion.
The Chief-SI Strain Measurement Solution
Our Chief-SI StrainMap integrates SCXI hardware and mechanics theory to calculate and present data in a user-friendly GUI including complete functions
and simple operations. Our solution has multiple advantages including high-precision and synchronized multichannel measuring equipment with ±3 υε at 2
k resolution sampling rate, a synchronized-sampling rate of 2 kS/s for the StrainMap and 50 kS/s for the StrainMap Enhanced, and a 128-channel
maximum.
In addition, our solution includes a simple hardware interface and friendly GUI for all required configuration with patented, plug-and-play style signal
terminals, a GUI to configure the setting, and IPC-9704 guideline support for PCB strain gage testing and other related techniques. Also, the real-time,
multichannel signal curve display and continuous data recording displays the strain signal curve of each channel display in real time and provides Mohr’s
circle function to show information about the maximum strain value and aspect.
The enhanced gauging efficiency and complete functionality for report generation supports main strain gaging report formats, states maximum and
minimum strain values for each channel, supports strain gage calculation, and directly offers strain measurement exporting to Microsoft Excel.
Furthermore, our solution offers dynamic strain measurement support with StrainMap Enhanced to accommodate a sampling rate up to 50 kS/s for faster
acquisition rates used in drop tests and simultaneously gauge the strain behavior and acceleration signal, which is in coherence with drop test standards.
We successfully delivered a complete strain measurement solution using LabVIEW, SCXI, and NI CompactDAQ so that companies in the PCB
motherboard and mobile phone-related industries, including Intel, HP, and Lenovo, could confidently adopt our SI StrainMap solution.
Author Information:
Alan Ho
Chief-SI (http://partners.ni.com/partner_locator/partner_details.aspx?id=92264)
No. 196, Wuhe Street
Whlong Village, Cyonglin Township
Taiwan
Tel: +886-3-5936268
Fax: +886-3-5936228
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The Chief-SI StrainMap integrates SCXI hardware and the theory of mechanics to calculate and present data in a user-friendly GUI, including complete functions and
simple operations.
Software based on LabVIEW in the StrainMap solution provides a user-friendly graphical user interface.
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