In ground testing, force measurement systems, typically referred to as “balances,” are state-of-the-art instruments used as the primary measurement device during wind-tunnel testing for high-precision aerodynamic force measurements. Fundamentally, nearly all force measurement systems—including balances and load cells—rely on strain-gage instrumentation in order to correlate applied loads with electrical response measurements.
Force balances are typically composed of complex spring elements that are designed to deform a specified amount under the influence of an applied load. The deflections of the balance under load result in a change in strain within the flexural elements, which are measured using Wheatstone bridges composed of foil resistive strain gages. Each of these Wheatstone bridges is designed to respond primarily to one of the six components of applied load. The electrical response of each strain gage bridge is directly proportional to the applied loads; this relationship is characterized during the instrument calibration process.
Developing force measurement systems that provide NASA/AETC capabilities for high-precision measurements and data quality requires that the instruments be designed taking into account several fundamental design factors:
- Understanding of Material Properties
- Structural Design Fundamentals
- Strain Gage Instrumentation Design
- Experimental Design Techniques for Developing Calibration Methodologies
- Fundamental Understanding of Calibration Capabilities and Techniques
- Data Analysis and Processing Skills
All of the work that AETC is doing in force measurement is handled by the National Force Measurement Technology Capability (NFMTC) in partnership with Test Technology. The NFMTC is a NASA-wide effort to rebuild sustainable workforce, hardware and infrastructure in the area of force measurement. Through support from AETC, the NFMTC office is currently reinvigorating the national leadership and competency in force measurement in order to retain the role as the national experts in this field.
Contact Information
Devin Burns at NASA Langley
Jonathon Ponder at NASA Glenn
James Bell at NASA Ames
