Measurement Uncertainty Sources Analysis And Evaluation Of Parasitic Time Grating Sensors

In order to improve the measurement accuracy, the error separation, correction, self correction methods are used for the newly developed parasitic time grating at present. But these methods can only be applied for the error correction, and the error sources of the time grating have never be analyzed before. So the error correction research results cannot be used to guide the sensor structure optimization design. In the development of the parasitic time grating sensor, the error and uncertainty sources are not analyzed in theory.In order to conduct systemic analysis the error and uncertainty sources of parasitic time grating sensors, and to improve its measuring accuracy, the 84-level parasitic time grating was used as the research object in order to establish the uncertainty evaluation system which met the international GUM standard. Based on the principle of the angle measurement and the motor, the traveling wave formula of the parasitic time grating sensor was derived. All factors affecting the measurement accuracy were analyzed from the part and the processing part of the traveling wave signal by using the magnetic circuit analysis method. Traveling wave signal generation part and corresponding processing error and assembling error of sensor, traveling wave signal processing section and corresponding sensor processing circuit error. The uncertainty sources of the time grating sensor was completed in theory.The important electromagnetic parameters were analyzed by Ansoft Maxwell to determine the main uncertainty sources by using the control variable method. The simulation results show that excitation signal frequency, the gap width, the relative area of the probe and the rotor are the major factors which influence the angular accuracy of parasitic time grating sensor. The number of coils, the excitation signal amplitude, the length of core are secondary factors.The angle calculation formula was analyzed according to its measurement principle, and the uncertainty sources were divided into four categories which include error of interpolation pulse, quantization error of interpolation pulse signal, periodic error of traveling wave signal, environmental error. The theoretical transfer relationship among different uncertainty components were used to deduce the formula for the calculation of the synthetic measurement uncertainty according to the modern uncertainty theory..The experimental platform was built to measure the specific value of the uncertainty components by using the oscilloscope measurement result evaluation. And the synthetic measurement uncertainty of the parasitic time grating sensors was calculated by using the above specific value of the uncertainty components which was compared with the actual sensor measurement error of the whole circumference. It can be seen that the uncertainty evaluation results by using the above built uncertainty evaluation method are consistent with the actual sensor error. Therefore, it can be used in the practical evaluation of the parasitic time grating sensor. The acquired results can be used to do the further research on the structure optimization, error correction and uncertainty analyzing of parasitic time grating.