ST350 Strain Transducer

ST350 Strain Transducer

The ST350 Strain Transducer was developed out of necessity in the early stages of BDI. Our field teams needed to quickly and accurately measures strain on a variety of structures in a way that no other product could. Now, nearly four decades later, the ST350 Strain Transducer is the gold standard in structural health monitoring, which promises the fastest setup times and most reliable readings.

The ST350 is a resistive-based strain gage, made up of a 350ohm full Wheatstone bridge strain transducer to provide accurate, reliable, readings. Cable entry into the aluminum enclosure is fully potted for a weatherproof product that performs in the harshest of field environments. With roughly 3.5 times the output of a typical foil gage, these reusable sensors are ideal for measuring live-load strain.

These sensors are designed to be the most rugged and easy-to-use strain gages on the market, allowing you to install them in minutes in any weather condition. You can use the ST350 to measure strain on steel, concrete, reinforced concrete, fiber reinforced polymers, and timber with our full suite of accessories and mounting options.

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Features – ST350 Strain Transducer

  • Cost-effective  
  • Installs in 5 minutes or less  
  • Reusable, lasts for >10 years  
  • Waterproof to 20ft (6 m)  
  • Industrial cable, custom lengths  
  • Standard millivolt output  
  • NIST-traceable calibration  


  • Steel
  • Pre-stress/post-tension concrete
  • Reinforced concrete
  • Timber
  • Fiber Reinforced Polymer (FRP)
  • Live-Load testing & monitoring
  • Laboratory testing
  • Fatigue monitoring
  • Tension rod forces


SPECIFICATIONS – ST350 Strain Transducer

CIRCUIT Full Wheatstone bridge with 4 active 350Ω strain gages
EXCITATION VOLTAGE +1.0 to +10.0 Vdc
OUTPUT mV level, ratiometric to Excitation Voltage
STRAIN RANGE  ±4,000 µε (Calibrated to ±2,000 µε)
EFFECTIVE GAGE LENGTH 3.0 in (76.2 mm) [Gage Extensions available for R/C structures]
HOUSING Machined 6061 Aluminum Alloy
CORROSION PROTECTION Hard Anodized Clear (MIL-A-8625 Type III)
WEATHER PROTECTION Designed to exceed IP67
Optional 100 ft (30 m), waterproofing available
TEMPERATURE RATING2 -58° to +176 °F (-50° to +80 °C)


1 Accuracy defined at the calibrated ±2,000 µε range.
2 Temperature limit based on instrumentation cable operating temperatures, call BDI for wide temperature range cable options.


Options & Accessories – ST350 Strain transducer