iTestSystem Tip: Strain Gauge Rosette Analysis

When troubleshooting structural failures or validating FEA models through testing, strain gauge rosettes are used to find the full state of strain at areas of concern around the structure.  iTestSystem’s Rosette Analysis tool is used to calculate the principal strain, principal strain angle, shear strain, principal stress, and other values from strain gauge rosette data. This video shows how to use the Rosette analysis tool.

For questions about using the Rosette Analysis tool or other iTestSystem analysis tools contact Chase Petzinger.

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iTestSystem Tip: Sensor Auto-zero Utility Update

Our iTestSystem customers who routinely acquire data with high channel counts and data from full-bridge transducers recently requested that we update the sensor auto-zero utility to improve test setup efficiency.   In the latest version of iTestSystem (16.1.0.29), we updated the sensor auto-zero utility to include all channels that use the From Custom Scale option.  This update enables users to quickly adjust selected channel offsets with only a few mouse clicks.

One of our test engineers recently used this feature to test and calibrate a new load cell design for measuring loads in a manufacturing process.  He was able to quickly calibrate and zero the strain gauges along with a calibrated load cell and a pressure transducer prior to testing and before each directional test. The offset values are included in the calibration data files for traceability.

Contact Information: For more information about this update or iTestSystem contact:

Chase Petzinger – Integrated Test & Measurement (ITM), LLC. Email: chase.petzinger@itestsystem.com or Phone: 1.844.TestSys

Roving Accelerometer Impact Tests with iTestSystem

3D Animator: Bike Frame Twist Vibration Mode at 26.2 Hz

In order to prevent or troubleshoot structural vibration problems, it is important to characterize a structure’s dynamic behavior using both experimental and Finite Element Analysis (FEA) technologies.  One method used to identify a structure’s vibration modes is to perform a roving accelerometer or roving hammer impact test.  In an impact test, engineers measure the response of a structure from an impulse delivered by a calibrated hammer using tri-axial accelerometers.

FRF View: Bike Frame Point 9 Coherence & Magnitude

Managing impact tests on large structures can be tedious and cost prohibitive, since they require collecting accelerometer responses at hundreds of locations to resolve the vibration motion.  Not only do test engineers need to keep track of the locations, they also need to keep track of the orientation that an accelerometer is positioned.

Our test engineers have found that the most efficient and cost effective solution for collecting impact data is to use a National Instruments (NI) cDAQ chassis with either NI-9234, NI-9232, NI-9231 or NI-9230 IEPE modules along with a calibrated impulse hammer and between 3 – 9 tri-axial accelerometers. To collect, manage, and visualize the modal data, our LabVIEW software engineers developed the Impact Test DAQ, FRF Viewer, and 3D Animator applications for our iTestSystem software platform. These applications incorporate tools that our test engineers need to manage and validate the quality of their modal data while in the field.

For more information about impact tests, modal analysis, our iTestSystem Impact Test applications, or to schedule a modal test contact Mark Yeager or Ryan Welker.

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ITM adds FieldDAQ Sound & Vibration Module compatibility to iTestSystem

The FieldDAQ™ FD-11634 sound and vibration input module from National Instruments (NI) can now be used with the latest version of iTestSystem (16.1.24).  The FD-11634 is similar to the NI-9234, NI-9232, NI-9231, and NI-9230 cDAQ dynamic input modules and can be used with IEPE type sensors such as accelerometers and microphones.  Like the other FieldDAQ™ modules, this module is IP65/IP67 dust and water resistant with an operating temperature range of  -40 °C to 85 °C.  Our test engineers would use these modules for collecting vibration data on mining and construction equipment, vibration data on rotating machinery within manufacturing facilities and test cells, and acoustic data for measuring equipment noise emissions.

The FieldDAQ™ FD-11634 module has 8 simultaneous sampled, ±1V or ±10 V, 24-bit differential input channels with AC/DC coupling. It has a maximum sample rate of 102.4kS/s and features built in anti-aliasing filters that automatically adjust to the sampling rate.

For advice about using the FieldDAQ™ FD-11634 sound and vibration modules in iTestSystem monitoring applications or with custom cRIO RT and FPGA control applications contact Mark Yeager or Chase Petzinger.

Click Here to view a video showing one of our test engineer collecting data from a submerged FieldDAQ™ module with iTestSystem.

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iTestSystem Tip: Impact Hammer Setup

While iTestSystem is designed to collect data from specific sensor types like strain, voltage, current, and accel; custom signal types such as pressure, displacement, and force can also be configured by utilizing the Custom Scale functionality during the channel creation process.

For example, manufacturers often need to measure the amount of force required to install a component using a calibrated impact hammer.  Since iTestSystem does not have a specific channel type for impact hammers, we must create one using a similar channel type.  The channel type most similar to an impact hammer is the accelerometer channel.1

Example Impact Hammer: PCB Model 086D20

To configure a piezoelectric impact hammer in iTestSystem, first create an accelerometer channel.  An accelerometer channel will supply the impact hammer with IEPE constant current.  From the accelerometer configuration window, change the Units to “From Custom Scale”, set the sensitivity to 1, and set the sensitivity units to Volt\g.  Next, set the custom scale: scaled units to lbs, lbf, or N, Prescaled Units to g, and in the slope field, input the lbs\Volt value from the hammer’s calibration sheet.  After entering these settings, be sure to hit the Test button to verify your signal and save the settings after verification.

Notes

  1. Most impact hammers are piezoelectric and require IEPE constant current excitation.  Several iTestSystem compatible National Instruments (NI) cDAQ input modules (NI-9230, NI-9231, NI-9232, and NI-9234) can supply IEPE excitation for an impact hammer.  These modules are typically used for piezoelectric accelerometer inputs.

For a free trial of iTestSystem including the custom scale settings or to learn more about impact hammer measurements, contact chase.petzinger@itestsystem.com.

Strain Gauge Shunt Equivalent Calculations in iTestSystem

When making strain measurements it is important to perform a shunt calibration both before and after the actual measurements are acquired.  Shunt calibrations ensure accurate strain measurements by adjusting the sensitivity or gain of the data acquisition equipment to compensate for leadwire resistance and other scaling errors.

iTestSystem takes advantage of the shunt calibration circuits included in the National Instruments (NI) cDAQ strain modules.  The NI-9235, NI-9236, and NI-9237 strain modules contain an internal shunt resistor that when switched on “shunts” across one leg of the strain circuit’s wheatstone bridge.  When active, the shunt resistor offsets the strain measurement by a constant strain which is calculated using the equivalent shunt calculation.  The equivalent strain/shunt value is dependent on the strain gauge configuration, gauge resistance, shunt resistance, gauge factor, and material properties.

In the latest version of iTestSystem we added a built-in strain gauge shunt equivalent calculator that can be accessed from the strain configuration page.  This calculator has allowed us to speed up the calibration process and eliminate hand calculation errors.

For a free trial of iTestSystem and the equivalent shunt calculation tool, contact chase.petzinger@itestsystem.com.

iTestSystem Update: Joint Time Frequency Analysis Tool

Over the past few weeks we have been updating our Joint Time Frequency Analysis (JTFA) tool for iTestSystem. In general, the JTFA tool is used to show how the frequency content of a signal changes over time. This tool is particularly useful for analyzing and visualizing vibration and strain data on rotating machinery.

After using the JTFA tool on an internal data analysis project with a colleague, we realized that with a few additions and changes, the tool’s capabilities and processing efficiency could be greatly improved. To achieve this, we added a configurable overall frequency band algorithm for trending frequency bands related to specific machine fault or vibration modes. We also added templates for quickly developing and switching between frequency band signatures and settings. Finally, we added the capability to export the results to a data file for later viewing in TestView Plus or Excel.

These changes are included in the latest version of the JTFA tool. For a free trial of iTestSystem and the JTFA tool, contact chase.petzinger@itestsystem.com.

ITM Live Demo Series: iTestSystem with NI FieldDAQ

As a part the ITM Live Demo series, we’re excited to release this video featuring iTestSystem and National Instruments FieldDAQ™ hardware.

At ITM, we’re always on the lookout for tools that will help us take tough measurements.  When we heard that NI was introducing a new device that features IP65/67-rated ingress protection, we were very excited.  In many industrial or off-way environments, there is potential for fluids to splash or leak onto exposed hardware.  Could the NI FieldDAQ™ be a solution for these types of environments?

Watch now as I demonstrate how to use an NI FieldDAQ™ Strain Device with iTestSystem and answer the question; Will it work while submerged in water?

If you’re interested in learning more about iTestSystem or FieldDAQ™, feel free to contact one of our test specialists by e-mail at info@itestsystem.com or phone at (844) 837-8797.

iTestSystem Tip: Start and Stop Tests with MultiDAQ Trigger

In iTestSystem use the MultiDAQ trigger function to automate data collection.  Follow the steps below to enable and configure triggering.
1. Enable auto save
2. Enable triggering
3. Build a start trigger statement
4. Build a stop trigger statement
5. Start configured MultiDAQ
6. Let MultiDAQ collect your data.

iTestSystem Tips: Modify Multiple Channels with Excel

 

Edit multiple channels at once by using excel. Highlight the Channels item in the configuration tree. Export the channels to a CSV file. Open the CSV file in Microsoft Excel, then edit and save. Import the edited CSV file to update the configuration file with the channel changes.