Our test engineers are often called upon to deploy unattended or “black box” data acquisition systems in the field. These systems are deployed on machinery, vehicles, and industrial processes to constantly record strain and vibration data at sample rates between 100 and 100,000 Hz. That adds up to a lot of data to sift through.
In situations where we are trying to identify system operation outliers or damaging events, we utilize the Automated Analytics application in iTestSystem to limit the amount of data searches required. The Automated Analytics application allows users to analyze, build, and send sensor level reports only when specific vibration and strain limits are exceeded. Instead of searching through data files, engineers can easily review the report and download relevant data files from deployed systems for further analysis.
This video demonstrates how to build and send vibration and strain reports using Automated Analytics and other iTestSystem tools and applications.
- Strain Gauge Installation for Field Testing
- General Purpose Accelerometers for Rotating Machinery Vibration Measurements
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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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, 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: firstname.lastname@example.org or Phone: 1.844.TestSys
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.
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.
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The FieldDAQ™ FD-11634 sound and vibration input module from National Instruments (NI) can now be used with the latest version of iTestSystem. 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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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
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.
- 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.
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.
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.