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Wireless Strain Measurements with iTestSystem, LabVIEW, and Arduino

On a recent project, one of our engineers needed to measure structural strain at several locations on mobile lifting equipment while in operation. Since the strain measurements were distributed and mobile, a wireless internet of things (IOT) solution was required. This blog describes the steps and tools we used to integrate our solution into iTestSystem and LabVIEW™.

One of the wireless devices that we evaluated to monitor strain was a SparkFun Thing Plus (ESP32 WROOM) with a Load Cell Amplifier (HX711). The SparkFun Thing Plus uses the Espressif ESP32 Wi-Fi and Bluetooth MCU. It accepts a variety of digital interfaces including high-speed SPI, UART, I2S, and I2C. The HX711 load cell amplifier accepts four-wire Wheatstone bridges and outputs 24-bit data at either 10 Hz or 80 Hz. The digital signal from the HX711 was connected to a GPIO pin and clock pin on the SparkFun Thing Plus.   We used a Lithium Ion 2Ah battery to power both devices.

Figure 1: Wireless Strain Prototype Connected to a 4-Wire Bending Bridge

After making the connections and installing the device in a 3D printed case for mobility testing, our development engineer programmed this device using the Arduino IDE. Our wireless strain prototype was programmed to auto connect to a Wi-Fi network and output device ID, tag names, and data values via UDP or Webservice. We chose UDP because we only needed the latest strain/load values. Bundling the device ID with the strain data would allow iTestSystem to collect data from multiple devices. To test the wireless strain prototype and develop the UDP interface for iTestSystem, we modified the Simple UDP LabVIEW example vi.

Figure 2: Arduino IDE with Example Program

Next, we integrated the wireless strain prototype into iTestSystem by adding a new communication class into the existing iTestSystem IOT Communication utility. This new class allowed the utility to read the specific UDP data type associated with our prototype and output data to a shared variable. Shared variables can be logged to disk and analyzed with iTestSystem alongside other machine data.

Figure 3: Simple UDP LabVIEW™ Code

For more information about this application, iTestSystem, or our strain gauging services, contact Mark Yeager via email at mark.yeager@iTestSystem.com or phone @ 1.844.837.8797 x701.

Troubleshooting Machine Failures Caused by Intermittent Damaging Events

Over the years we have been tasked with identifying the root cause of machine structural failures. In many cases, we can determine the failure mode through strain and vibration testing, order analysis, modal analysis, and operating deflection shape analysis.  What tests can you run when the damaging conditions are intermittent and not easily identified?

In these cases, we like to install a cellular networked temporary data acquisition (DAQ) system that can autonomously log vibration and strain data along with machine status data. We have deployed two types of DAQ systems to collect data remotely.  An interactive system that includes an industrial PC running our iTestSystem software and National Instruments (NI) Compact DAQ hardware and a headless system that utilizes NI Compact RIO hardware.  Our test engineers prefer using the interactive solution for troubleshooting because they can view real-time signal waveforms and collected data files, and then adjust the test parameters accordingly without having to reprogram the hardware.

Figure 1: Headless networked data acquisition system

When potentially damaging events are identified in the vibration and strain data collected by these systems, it is important to know the machine’s operating status. Collecting the machine status information is just as important as collecting the structural data.  Many machines transmit these operating variables and operating stages over their network/bus.  Recently we have recorded process data from Allen Bradley Control Logix PLCs via Ethernet/IP, mining machine data from a Siemens controller via proprietary TCP/IP protocol, boiler condition data from a DCS via Modbus TCP,  machine pressures from PI historian via the UFL connector (TCP), and vehicle speeds and pressure via CAN.  Fortunately, we were able to use and adapt LabVIEW communication protocol tools to build applications and addons that allow this network tag data to be collected along with structural data.

Figure 2: Modbus to Shared Variable Tool

After the data collection phase, our engineers perform statistical analysis on the sensor and status channels in all data files and aggregate the results into a database for searchability. To identify the root cause probabilities, you can process the channel statistics data using your favorite correlation algorithm or application.  The image below shows an example data set containing related sensor data that was processed using a LabVIEW correlation test tool.

Figure 3: Correlation Test Example vi

Contact Information: For more information about our remote data acquisition service, our LabVIEW development service, or iTestSystem contact:

Mark Yeager – Integrated Test & Measurement (ITM), LLC.  Email: mark.yeager@itestsystem.com or Phone: 1.844.TestSys

ITM adds NI-9253 Compatibility to iTestSystem

This week we added another module to the iTestSystem compatibility list.  One of our iTestSystem users recently needed to collect data from thirty-two (32), 4 to 20 mA current sensors along with their vibration measurements.  National Instruments (NI) recently introduced a new C-Series current module, the NI-9253, that was a perfect fit for this application.

The NI-9253 module has eight (8) simultaneous sampled (50kHz max), +-20 mA, 24-bit input channels.  It has several diagnostic features to ensure your system is operating nominally at all times with open channel detection, power supply detection, and configurable thresholds. The NI-9253 has eight LEDs that indicate the status of each channel and the power supply so a user can easily determine the system’s status in the field.  The NI-9253 also features a number of programmable hardware filters (Butterworth and comb) to reduce signal noise.

Click Here for more information about iTestSystem.

For advice about using the NI-9253 versus other current modules in iTestSystem monitoring applications or with custom cRIO RT and FPGA control applications contact Mark Yeager or Chase Petzinger.

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.

Click Here to download iTestSystem

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.

Click Here for more information about iTestSystem.

ITM @ VIATC 2019: Vibration Institute Annual Training Conference

Come see us at the VIATC 2019 Exhibit Hall in Booth 33!

Ryan Matthews and Mark Yeager (CAT III Vibration Analysts) will be there to answer questions about our iTestSystem engineering measurement platform, our on-site testing services, LabVIEW consulting, and strain gauging services.

When: July 24 & 25th

Where: The VIATC 2019 conference and exhibit hall will take place at the Lexington Center, connected by a joint lobby to the Hyatt Regency Lexington.

Lexington Center
430 West Vine Street
Lexington, KY 40507

Silo Load Monitoring

Plant operators need to continuously measure bulk material levels/weight to make sure their processes are running safely, efficiently and without any bottlenecks. Measuring these levels allows operators to automate vessel filling/emptying logistics or verify that a process is using the right amount of material.

How do you measure bulk material levels/weights in silos and hoppers?

There are a variety of bulk material level/weight monitoring sensors in the market. These sensors include distance measuring devices like laser, ultrasonic, and radar; or weight measuring devices like load cells and strain gauges. Our engineers prefer to implement strain gauge based solutions because they are very accurate and do not require structural modification.

For these solutions, our engineers identify the silo/hopper load paths and our technicians install strain gauges at these locations. By calibrating the strain gauge sensors to load and summing the load data for all load paths, we can accurately measure the total weight of the bulk material.

A typical silo monitoring system consists of weatherproofed strain gauges for each silo leg and a National Instruments (NI) CompactRIO embedded controller for inputs, calibration, and outputs housed in a stainless steel enclosure.

For more information about silo monitoring, contact Ryan Welker @ 1.844.837.8797 x702.  To see how ITM’s structural load monitoring systems work watch this video.

video link: https://youtu.be/TwVtDYLkFKs.