Restoring the Instron Laboratory Testing Machine with NI LabVIEW and Data Acquisition Hardware

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"Our testing machine has been upgraded with a PC-based data recording and storage system, which offers high-quality test data that is more accessible to students than it was with the original system."

- Jim Mooney, University of West Scotland

The Challenge:
Restoring an outdated materials testing unit in a university laboratory that was deemed unserviceable.

The Solution:
Using National Instruments data acquisition devices and the NI LabVIEW graphical programming environment, we were able to upgrade the outdated, idle system to a PC-based test and data acquisition environment.

Jim Mooney - University of West Scotland

The Instron Model 1105, a 10-ton capacity testing machine at University of the West of Scotland, has been used by staff and students in the material testing laboratory since 1972 for tensile and compressive testing of material specimens. Material specimens are subjected to either tensile or compressive loads and are tested until they fail.

The original measurement system consisted of a strain bridge, an amplifier, and a chart recorder. Test results were plotted on the chart recorder in the form of a load versus extension graph, and the graph was then analyzed using traditional graphical methods to determine material properties.

In 2001, the amplifier unit failed and the machine remained idle until 2006. Without the Instron machine, material tests were conducted on a smaller capacity testing machine, which limited the range of tests that could be undertaken. Following an inquiry to National Instruments regarding a solution to this problem, a field engineer visited the campus and suggested a PC-based data acquisition solution using NI software and hardware that could repair the testing machine.

Refurbishing and Automating the Outdated Test System

The original load cell unit was checked by the NI engineer and found to be serviceable; therefore, it was decided that it should be retained as part of the new system. The valve amplifier and associated hardware was removed from the carcass of the testing machine and modifications were made to accommodate the PC-based system consisting of an NI PCI-6251 M Series data acquisition board, an NI SCC-SG24 strain gage amplifier, and LabVIEW software.

We removed the original chart recorder and fit a flat screen monitor into the recorder cabinet. We also installed a color printer to produce hard copies of test results, and we fit an easily accessible USB socket at the front of the testing machine for data transfer to portable storage devices, so students can take electronic copies of the test results with them.

The output of the load cell is 10 mV at the maximum load of 10 tons. The inherent filtering characteristics of the original valve amplifier enabled the output of a high-quality signal to the chart recorder. Initially following the upgrade to a PC-based system, the output signal from the SCC-SG24 strain gage amplifier was buried in noise; however, National Instruments engineers suggested a software-defined, signal-conditioning solution and a high-quality output signal was achieved.

Recording and Analyzing Test Data with LabVIEW

The LabVIEW graphical development software provides an ideal platform to display and record test data from the Instron testing machine. Test results can be saved to a spreadsheet VI for analysis purposes, so students can make comparisons of material properties by displaying results in a graphical format.

The testing machine is in service again and is used on a regular basis for laboratory work. The original measurement system provided a single paper copy of a test, whereas the upgraded system produces personal copies of test data for each student to analyze and display in a word-processed report. We intend to integrate the Instron PC with the university network to permit additional users access to test data form the testing machine.

The Instron testing machine, which was rendered unserviceable with a failed amplifier unit, was restored to full working order. It has been upgraded with a PC-based data recording and storage system, which offers high-quality test data that is more accessible to students than it was with the original system. Additionally, by retro-fitting NI software and hardware to this machine rather than purchasing a replacement, approximately £10,000 was saved.

Author Information:
Jim Mooney
University of West Scotland

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