An application note that explains strain, gauge factors, bridge configurations, wiring, and signal‑conditioning using NI SCXI modules.
This tutorial introduces the concept of strain and the gauge factor of metallic strain gauges, describing how strain is expressed and measured. It covers the use of Wheatstone bridge configurations—including quarter‑, half‑, and full‑bridge circuits—and methods to reduce temperature effects such as dummy gauges.
The note also details signal‑conditioning requirements, including bridge excitation, remote sensing, amplification, and offset‑nulling techniques. Specific NI SCXI modules (SCXI‑1121, SCXI‑1122) and the low‑cost SC‑2043‑SG conditioner are described with their features and example system configurations for acquiring strain gauge data.
| SCXI‑1121 number of channels | 4 |
|---|---|
| SCXI‑1121 excitation voltage source | 3.333 V or 10.0 V |
| SCXI‑1121 amplifier gain range | 1 to 2000 |
| SCXI‑1121 half‑bridge completion | Yes |
Using a dummy gauge or a half‑bridge configuration with a dummy gauge cancels temperature‑induced resistance changes.
Excitation voltages of around 3 V and 10 V are common.
The SC‑2043‑SG module provides an eight‑channel low‑cost signal conditioner.