Study on the Uncertainty of the Doppler Frequency for the Calibration of LDV within the Speed of (0.1~340) m/s
Abstract
Laser Doppler Velocimetry (LDV) is a single-point velocity measurement instrument. LDV can be precisely calibrated by the adjustable speed spinning-dics facility from NIM at speeds generally less than 40 m/s. However, due to its unique limitations, it is hard to calibrate LDV at a higher speed. To solve the problem of traceability of LDV high-speed measurement results and of the applicability of LDV low-speed calibration results under high-speed conditions, it is analyzed that the uncertainty of velocity depends on both interference fringe spacing and Doppler frequency. As fringe spacing is independent of velocity, the possible difference of uncertainty in between the high and low velocity may be only related to the uncertainty of Doppler frequency at different velocities. Doppler frequency is a result of Doppler frequency algorithm, which includes mixed-radix FFT (Fast Fourier Transform) and the phase difference correction method in this paper. Because of the nonlinearity and complexity of the algorithm, the uncertainty of Doppler frequency is suitable for being evaluated by Monte Carlo Method (MCM) propagating probability distribution. The evaluation result shows that the relative uncertainty of Doppler frequency caused by the algorithm is less than 0.05 % within the range of (0.1 ~ 340) m/s. The obvious difference of uncertainty has not been found in different velocities investigated. The budget resulting from Doppler frequency uncertainty change on the velocity result is less than 0.00075 %. It is concluded that the calibration result at low velocity is also reasonable to be used in the case at the high velocity measurement within the speed of (0.1 ~ 340) m/s.
Event details
- Event
- FLOMEKO 2022
- Technical Committee
- TC9
- lich@nim.ac.cn
- Place
- Chongqing, CHINA
- Time
- 1 November 2022 - 4 November 2022
- Website
- http://flomeko2022.msmk.tech/c/index.html