Campbell Scientific ST350 Strain Transducer for Structural Testing - Manual (Page 14)

Section 4. Wiring
4-2
tension provides a positive output signal and compression a negative signal. If
a tension force provides a negative signal (and vice-versa), the user should
either switch the signal leads or make appropriate adjustments to the signal
conditioning.
Before going to the field, Campbell Scientific highly
recommends that a simple validation be performed by the user to
ensure that signal conditioning, gains, and calibration factors are
being properly applied.
Please see informational write-up entitled “Verifying the Accuracy of ST350
Strain Transducers – Appendix B” on some of the things to look out for while
running your own calibration verification.
NOTE