Historical Technology Overview


Micro-Miniature Stress Analysis and Forecasted Endurance

MicroSAFE is a miniature Smart Sensor that measures and processes strain data using the ASTM Rainflow Cycle Counting Algorithm. The result of this algorithm is a histogram showing the number of deflections at different stress levels. Over 1 year of processed data can be stored internally in non-volatile memory. The standard battery (not pictured) allows for over 45 days of 24-hour acquisition and processing. Raw strain data is available to the user to verify the processing and to assure proper strain gauge installation.

Communication with the unit is through a special interface cable to a standard RS-232 port on a PC. A Graphical User Interface (GUI) handles programming, downloading, and graphical data representation.

The Rainflow Cycle Counting Algorithm summarizes irregular load-versus-time histories by counting the number of times that cycles of various stresses occur. Not only is this a highly effective data compression scheme, it graphically illustrates the movement of the material along the stress-strain curve. These excursions on the curve can be quantized and used to determine life expectancy

The histogram below represents the processed results of data acquired on the Fred-Hartman Bridge over the Houston, TX, ship-channel for a 35-minute period on July 23, 2002. Click on the graph for a larger picture.

Various external battery capacities are available.

  • Sample Rate: 32Hz
  • 1 external sensor per unit
  • MicroSAFE can support any resistive sensor type
  • Approximate Size: 2.5cm x 2.5cm x 3cm (pictured external battery version).

View the full MicroSAFE Technology Profile (MicroSAFE.pdf)