Calibrating laser Doppler anemometers utilizing an optical chopper

Published

January 31, 2025

Author(s)

Christopher Crowley, Iosif Isaakovich Shinder, Michael R. Moldover, Joey Boyd, James Filla, Aaron Johnson

Abstract

Laser Doppler anemometers (LDAs) use scattered light to determine velocity components of a flowing fluid. The operating principal of LDAs is simple conceptually; however, it is impractical to trace the LDA-determined velocities to the SI by characterizing the LDA's subsystems that generate, detect, and process optical signals because these subsystems are complex and include proprietary features. To circumvent this, we calibrated the complete LDA systems utilizing an optical chopper blade as an accurate, SI-traceable velocity standard. The calibrations achieved the expanded velocity uncertainty 0.094 % at a 95 % confidence level. We calibrated two LDAs that differed in manufacturer, focal length (in the ratio 3.3:1), sensing volume (in the ratio 100:1), and orientation (vertical and horizontal bisectors of the LDA's crossing beams). To compare the calibrations, we measured airspeeds in NIST's wind tunnel using both LDAs. The results differed from each other by, at most, 0.2 % throughout the airspeed range (0.5–30) m/s.

Citation

Metrologia

Volume

62

Issue

2

Pub Type

Journals

Download Paper

https://doi.org/10.1088/1681-7575/adac64

Local Download

Keywords

Laser Doppler Anemometer, Laser Doppler Velocimeter, Air speed measurements, airspeed standard

Citation

Crowley, C. , Shinder, I. , Moldover, M. , Boyd, J. , Filla, J. and Johnson, A. (2025), Calibrating laser Doppler anemometers utilizing an optical chopper, Metrologia, [online], https://doi.org/10.1088/1681-7575/adac64, https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=958360 (Accessed March 14, 2025)