Video GaugeTM - How it works

Imetrum® grew out of work done at Bristol University from the 1980s onwards in image processing for deflection and strain measurement, with a particular focus on real-time high speed measurements outdoors. The company was founded in 2003, after a breakthrough was made in sub-pixel measurement resolution enabling the technique to become a viable method for measuring properties of composite materials.

Video GaugeTM, the software at the heart of our systems, gives highly accurate measurements saving users time and money in their testing regimes.

Principles

The fundamental principles behind Imetrum’s® technology are often referred to as Digital Image Correlation (DIC). DIC is a way of taking precise measurements using cameras. It is used by engineers across many disciplines as a way of quickly identifying strains and displacements across a region of interest or a whole object, without altering the test results by attaching physical sensors such as strain gauges and LVDTs. It can provide rich data in a quick, easy to interpret way. DIC can be used for many measurements including identifying locations of high strain, measuring global deformation and scanning areas to identify the early onset of cracks. It is also commonly used to verify finite element analysis.

The origins of video based measurement can be traced to 1940, with early work on DIC done in the 1950’s. The technique has now become an accepted measurement tool in experimental mechanics. To calculate measurements, a grid of sub-images (each 21 × 21 pixels, say) is defined and the pattern within each one recorded. This pattern’s movement relative to the previous frame can then be calculated. Even with recent advances in camera technology, in order to do this at a useful resolution for engineering measurements, this pattern matching needs to be done at a sub-pixel level.


Features and benefits

Imetrum® were the pioneers of point to point precision measurement using video. Building on this heritage, Imetrum’s systems have a number of benefits that enable them to stand out from the crowd.

  • The highest resolution measurements, with proprietary DIC algorithms that can detect displacements smaller than 1/200th of a pixel and strains smaller than 3 microstrain (point-point) and 50 microstrain (full-field).
  • Fast analysis of results – with our origins in image processing stemming back to the 1980’s, creating the most efficient processing algorithms is part of our DNA – this allows us to do real time analysis of videos, as well as multiple simultaneous strain maps.
  • Less time and effort spent getting the pattern and lighting right – our algorithms are designed to be unfussy when it comes to getting the right pattern, and are frequently used on natural surfaces.
  • You don’t need to have a PhD to get accurate results from an Imetrum system. We work hard to provide the easiest to use interface possible for strain maps, enabling speedy test setup and simple operation.
  • Time synchronisation with almost all other measurement systems and sensors.

Benchmarking

Imetrum’s® software has been independently benchmarked to be an order of magnitude more accurate than other DIC software when applied to real, physical objects. There are two ways this measurement capability can be delivered and Video Gauge™ offers both in one package:

  • a point based approach to mimic traditional gauges
  • creating colour maps of strain and displacement.

Point-point virtual measurement gauges are equivalent to traditional devices - simple to use with real-time outputs (up to 1kHz), but there is no extra cost to adding gauges. Simple calibration tools mean 2D measurement is possible in minutes, with 3D measurements available straight out-of-the-box. Maps can identify stress concentrations and cracks, and run simultaneously with gauges.

For more information, contact your local Imetrum representative or view our product page and look at our product information sheets.

Videos

Introduction to Video Gauge