Fundamentals of Strain Gage Measurements
Introducing the Industry's First Safety Critical Multiplexer Module
Introducing the EMX-1434: "Smart" PXI Express Source/Tach Module
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Strain gages and other bridge-type sensing devices like load cells, torque, and force sensors are used extensively in structural test and monitoring applications. As lighter, stronger materials continue to expand the performance envelope of products ranging from aircrafts to automobiles, structural measurements are increasingly crucial for testing and characterizing these products. Additionally, our world is full of structures such as bridges, wind turbines and even roller coasters that must be monitored or periodically evaluated to ensure key safe-operation criteria are met.

This guide provides a practical introduction to strain gage measurements with easily understandable, yet detailed information on how strain gages work. It also explains how strain measurements are made, and provides practical considerations for achieving high-accuracy strain measurements.

For additional information on strain gage measurements, please contact VTI Instruments. Our experienced team of Applications Engineers will be able to guide you.
The EX1200-2087A is the first multiplexer switch module in the industry with built-in failsafe monitoring, offering assurance and guarantee that make it ideal for safety critical applications where cost of failure can be high, for example:
  • Aircraft power distribution systems testing
  • Electrical safety testing
  • Insulation testing
When high voltages are switched through relays, the potential difference between the contacts can cause arcing which can melt a small section of the contacts. If the contacts are still closed when the molten section solidifies, the contacts may weld together and damage the relay. While this is not a common occurrence, welded contacts could cause signals to be routed when not intended and could affect the test system or the unit under test.
The EX1200-2087A is a high-voltage multiplexer with a built-in failsafe monitoring mechanism that continuously monitors the relays to ensure contacts haven't been welded shut and the unit under test isn't exposed to unintended connection paths.
The built-in failsafe monitoring mechanism works using internal relays to route current from an internal current source through the signal path to a comparator which measures voltage drop across the path. When failures are detected, interrupts are generated that can immediately stop the test.

Visit our website for more information.

VTI is pleased to introduce the latest addition to our SentinelEX data acquisition family - the
EMX-1434 "Smart" PXI Express 4-channel arbitrary source with 2-channel tach. This card is specifically designed for noise and vibration applications and is capable of providing stimulus to shakers, speakers and other electrical devices with built-in safety features like graceful shutdown. Each arbitrary source channel features 24-bit, 204.8 kSa/s data rates and industry leading -115 dB spurious free dynamic range (SFDR). Various output modes such as sine, burst-sine, chirp, burst-random and continuous random are supported in addition to custom-defined waveforms.
The EMX-1434 tightly synchronizes with other SentinelEX family products - the EMX-4250 and EMX-43x0 digitizers, forming a versatile dynamic signal analysis system that allows users to combine the required source and signal analysis in one chassis. Along with the 64-bit tachometer/counter channels, the EMX-1434 is ideal for a wide range of applications including rotational machinery analysis, order analysis, vibration control, impact testing and modal analysis.
Want to learn more about the latest and greatest solutions for structural dynamics testing? Visit our booth at IMAC to see what's in store for 2013.

IMAC XXXI - February 11-14, 2013
Hyatt Regency Orange County , Garden Grove, CA. Booth 207

VTI is proud to be a part of the US Navy's eCASS system – the most powerful ATE system in the world. eCASS replaces CASS as the US Navy's core test system and ensures that fleet aircraft can maintain mission-ready status by facilitating quick diagnostic and repair of line-replaceable subassemblies. Extending on our reputation as a premier supplier of core ATE switching systems, VTI's award winning EX1200 series forms the core of the eGPI (Enhanced Switching and General Purpose Interface) subsystem which provides signal switching and routing throughout the eCASS system.

At VTI, we view signal switching subsystems as a precision instrument and not just a collection of relays on a card. The quality of a switch is not determined by what it does, rather by what it doesn't do; the ideal switch instruments transmit signals exactly as they come in, without attenuating, adding noise, or reducing signal integrity in any way. Adopting this approach allows our switching solutions to maintain signal transparency, providing the highest level of signal integrity, which was essential for this application.

The eGPI subsystem leverages VTI's successful implementation of CASS compatible switching
for the RT-CASS program, and is designed to
improve the maintainability of ATE systems. This innovative approach allows the Navy to maintain
its large install base of legacy test program sets (TPS) while creating the flexibility required to support
next generation programs.
At VTI, we don't make statements lightly. When we say the CMX09 is the most advanced 9-slot PXI Express mainframe available in the market, we say it with the data to back it up. See for yourself:
Information on PXIe-1082 obtained from National Instruments website: PXIe-1082 2011-06-13 datasheet
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