Strain Gages / ST350
ST350 Strain Transducer


The ST350, manufactured by Bridge Diagnostics, Inc., is a strain transducer used to evaluate live-load stresses on structures such as bridges, buildings, cranes, and amusement park rides. It is prewired to connect directly with our dataloggers, and is ideal for structural monitoring data acquisition systems.

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Benefits and Features

  • Improved signal-to-noise ratio means higher-resolution measurements
  • Rugged enough for harsh environments
  • Pay for themselves with just a few uses
  • Compatible with most Campbell Scientific dataloggers
  • Quick installation with minimal preparation
  • Efficient, reliable, and highly accurate


Detailed Description

The ST350 uses Wheatstone bridge circuitry, which converts small changes in resistance to an output voltage that our dataloggers can measure. Its construction avoids the tedious and time-consuming effort required when using foil strain gages. This allows the ST350 to be installed within minutes on steel, concrete, timber, and FRP members.



Accuracy ±2% (individually calibrated to NIST standards)
Force Required for 1000 με ~17 lb (76 N)
Strain Range ±2000 με
Sensitivity ~500 με/mV/V
Circuit Full wheatstone bridge with 4 active 350 Ω foil gages, 4-wire hookup
Cable BDI RC-187 (22 gage, two individually-shielded pairs with drain; 15-ft length standard)
Material Aluminum
Dimensions 11.1 x 3.2 x 1.3 cm (4.375 x 1.25 x 0.5 in.)
Weight 85 g (3 oz)



The ST350 is affixed to steel, pre-stressed concrete, or wood via two threaded mounting tabs and a tab jig. Alternatively, two c-clamps may be used to mount the sensor to steel. Attachment to reinforced concrete typically requires two threaded mounting tabs, a transducer extension, and an extension jig.

Datalogger Considerations

Compatible Contemporary Dataloggers

CR200 Series CR800/CR850 CR1000 CR3000 CR9000X

Compatible Retired Dataloggers

CR500 CR510 CR10 CR10X 21X CR23X CR9000 CR5000 CR7X

Frequently Asked Questions

Number of FAQs related to ST350: 4

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  1. Customers have reported using the ST350 in applications similar to this.

  2. Generally, the recommended maximum strain for the ST350 is approximately 1,000 microstrain because of real-world installation conditions. The gage itself is capable of a higher microstrain measurement. For information regarding microstrain limits, refer to the “Instructions for Using ST350 Strain Transducer Extensions on Reinforced Concrete Structures” section in Appendix A of the “ST350 Strain Transducer Instruction Manual.”

  3. Use the full-bridge instruction, BrFull(). An example program for the CR1000 can be found in the “Datalogger Programming” section of the “ST350 Strain Transducer Instruction Manual.”

  4. The ST350 is designed as a full-bridge strain transducer with four active elements that can be directly connected to a datalogger (or a multiplexer connected to a datalogger) without adding a completion module such as the 4WFBS350 or 4WFBS120.