Posts

ITM Gathers Dam Spillway Data During Midair Strain Gauge Project 

Garrison Dam

Suspended in a harness 30 feet above a concrete spillway in central North Dakota, ITM engineer Ryan “RJ” Matthews instruments the gate of one of the world’s largest earthen dams with dozens of strain gauge sensors. 

Integrated Test & Measurement’s field service technicians and engineers have installed strain gauges on civil structures and machinery around the globe for decades, and this project represents one more example of rugged data acquisition. In this instance, the team rappelled from an overhead abutment on the Garrison Dam — a 2-mile-long structure along the Missouri River built by the Army Corp. of Engineers starting in 1947. 

Contracted by Cotech IRM Services, ITM was charged with collecting data to measure the strain on one of the 28 spillway gates which are designed to raise and close to allow water to pass from the reservoir during rare flood events. Just behind those gates is Lake Sakakawea, one of the largest man-made lakes in the United States. 

Garrison Dam Spillway

Despite the complex location, Matthews and co-worker Zach Strong were able to successfully instrument the spillway gate with 44 single-axis strain gauges and solder signal cables which lead back to a NICompactDAQ system connected to their laptop, allowing them to successfully gather streams of crucial data using iTestSystem while the gate was put through its paces.

The project is yet another example of ITM’s ability to combine the use of strain gauge sensors, a cDAQ system and the firm’s iTestSystem software to create a structural health monitoring system. In this instance, the project required only one-time testing, but ITM can also establish a permanent structural health monitoring system as well. iTestSystem is an engineering measurement software platform that enables test engineers to organize, acquire, view, and analyze data from machinery, processes, vehicles and other complex systems.  iTestSystem was specifically designed for use with National Instruments (NI) cDAQ hardware for data collection and data logging. 

For Matthews, it was his first experience installing strain gauges while strapped into a bosun’s chair and dangling in midair, but he points out that ITM’s strain gauge process is essentially the same whether their engineers are standing on a bridge or inside a railcar.  All that changes is the method of access and environment. 

His field notes reveal that each strain gauge on this job was wired in a quarter bridge configuration, which provides one individual measurement of strain (positive tension or negative compression) per location. All gauges were adhered to the gate using M-bond 200 epoxy.  A final report submitted to the customer contained detailed instrumentation and test notes and results reported in a series of stress/strain tables and stress graphs.

Contact ITM for your Strain Gauge Needs 

Installing strain gauges in the field for structural and fatigue measurements requires expertise and experience.  Whether you use our iTestSystem software to stream and analyze strain signals for static measurements and real-world fatigue data acquisition or contract our software engineers to build a real time strain monitoring system, we will make sure you acquire quality strain data. Contact our strain lab and technicians to install strain gauges on test specimens or to design, build, calibrate, and test strain-based load cells.

Strain Lab Contact Info: Ryan.Welker@iTestSystem.com, (844) 837-8797

 

High Channel Count Synchronous Datalogging

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…

Engineering Data Acquisition Tools: NI-9236 Strain Module

NI-9236 Strain Gauge Module

The most common strain gauge installation configuration is a 350 ohm, quarter bridge.  Quarter bridge installations a generally the easiest and most economical installation for determining structural strain levels.  In the quarter bridge configuration a single element strain gauge is mounted in the principle axial or bending strain direction.

One tool that our engineers and technicians use to collect data from 350 ohm, quarter bridge strain gauge installations is the NI-9236 strain module.  The NI-9236 is an 8-Channel C Series 350 ohm strain/bridge input module that is used with a CompactDAQ or CompactRIO chassis.  This module provides bridge excitation (3.3 Volts), Wheatstone bridge completion, shunt calibration, and filtering for 350 ohm quarter bridges.  Use this module in conjunction with a CompactDAQ chassis and iTestSystem engineering measurement software to collect synchronized, high-speed (10kHz) structure strain data.

For more information about the NI-9236, DAQ module rental, strain gauge installations or our data logging solution iTestSystem, contact Ryan Welker via email: ryan.welker@itestsystem.com or phone: (844) 837-8797 x702

Lattice Boom Crane Structural Design Validation

A case study describing a strain gauge DAQ system used to validate several new designs of a heavy lift lattice boom crane to comply with SAE J987 standards.

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, 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

Strain Gauge Installations for Field Testing

Image1: Shaft torque strain gauge installation example for field testing

Our engineers and technicians have epoxied, soldered and spot welded strain gauges for applications ranging from high temperature exhaust systems to miniature load cell measurements. Every application requires a unique understanding of the strain measurement requirements including installation environment.

If the strain gauge installation is to survive in the field you must plan for the conditions it will undergo. Three important variables that you should account for are temperature range, liquid exposure, and potential impact forces. These variables determine the type of strain gauge, epoxy, solder, wiring, coating, and impact/wear protection to use in the application. The table below shows which variables affect your installation choices.

  Gauge Epoxy Solder Wiring Coating Covering
Temperature  
Liquid Exposure      
Impact Forces      

Table1: Strain gauge installation variables

For more information about ITM’s strain gauging services contact Ryan Welker at email: ryan.welker@itestsystem.com or phone: 1.844.837.8797 x702