You might call it a more holistic approach to structural testing. Faced with the challenge of testing a large and complex on‐highway vehicle, engineers from Integrated Test & Measurement knew it would take hundreds of channels of data to measure the loads the 38‐ton piece of equipment undergoes while in use.
They further knew that their tests would be more efficient and reveal an even more accurate picture of the industrial unit at work if they could engineer a way to gather that data — more than 200 channels of accelerometer and strain gauge signals, plus speed and GPS metrics — all at once, allowing for complete synchronization.
Synchronizing such a high channel count was a challenge for which ITM was perfectly fitted and the very reason the Milford, Ohio, firm was subcontracted by SixDOF Testing & Analysis, which was hired to validate the design of the multi‐million dollar piece of equipment. Using a combination of National Instruments hardware — chiefly the NI 9469 Sync Modules and NI cDAQ‐9188 Chassis (or an NI cDAQ-9189 with built in sync) — ITM Engineer Todd Holtkamp “daisy‐chained” six chassis loaded with NI accelerometer and strain gauge modules. In theory, the configuration would enable an at‐once gathering of all the channels, but only if ITM’s proprietary iTestSystem software and MultiDAQ Plug‐in could handle the flood of information.
Once the instrumented operational and transport tests began, ITM’s software and plug‐in didn’t disappoint. It was the firm’s first in‐the‐field test to synchronize such a high channel count, and it performed precisely as they had hoped.
“I was blown away that the iTestSystem software could keep up with all the data that was coming in,” said Holtkamp, who described sitting inside the cab of the truck so he could monitor the test data real time while motoring down various road surfaces. “We had 200 plus channels coming into the software, and we were sampling at about 2,000 samples per second per channel. I was just amazed how fast the software was responding and updating.”
Even during the road tests — which required running all the test equipment from rechargeable batteries — Holtkamp was able to virtually look at every single channel from which they were gathering data to confirm they were getting good data.
The real‐time monitoring of the tests impressed SixDOF Project Manager Garth Wiley.
“ITM’s software provides ways of looking at a large number of channels to give you a first‐level quality check of the tests,” he said. “Sometimes a sensor might go out or a strain gauge might be too close to the exhaust system and burn out. So the software was real useful in allowing us to be able to look and see if any of the channels looked dead.”
Wiley also stressed the importance of the high channel count ITM delivered.
“You want to gather as much data as you can so you have a complete cross‐section of operating conditions and a good statistical sampling,” he said. “With a high channel count, you get to investigate more. If you want a complete picture, you need a large number of measurements.”
Synchronizing all the data, Wiley explained, not only saves the client time and resources — since they don’t have to tie up the equipment repeating multiple tests — but more importantly, it delivers better results.
“We like to be able to create an image of how a structure is moving at different frequencies,” said Wiley. “You can only do that if the data is all synchronous. You’ll never get anything that means anything in terms of a picture of how things are flexing and moving and vibrating without synchronized data.”
In the end, after about 10 days of data collection, ITM and SixDOF gathered around 20 gigabytes of information, which SixDOF then analyzed and ultimately delivered recommendations to the manufacturer for structural improvements.
Author Information: For more information about this Case Study, our Testing Services or iTestSystem (our data logging application) contact: Todd Holtkamp ‐ Integrated Test & Measurement (ITM), LLC – todd.holtkamp@iTestSystem.com