scholarly journals Error Correction of Water Vapor Radiometers for VLBI Observations in Deep-Space Networks

Atmosphere ◽  
2021 ◽  
Vol 12 (12) ◽  
pp. 1601
Author(s):  
Houcai Chen ◽  
Junxiang Ge ◽  
Qingde Kong ◽  
Zhenwei Zhao ◽  
Qinglin Zhu
Keyword(s):  
Water Vapor ◽  
Measurement Errors ◽  
Measurement Accuracy ◽  
Calibration Method ◽  
Absolute Calibration ◽  
Calibration Error ◽  
Ambient Conditions ◽  
Gain Error ◽  
Error Calibration ◽  
Water Vapor Radiometer

In this paper, we present the design and implementation tests of a water vapor radiometer (WVR) suitable for very long baseline interferometry (VLBI) observation. We describe the calibration method with an analysis of the sources of measurement errors. The experimental results show that the long-term measurement accuracy of the brightness temperature of the water vapor radiometer can reach 0.2 K under arbitrary ambient conditions by absolute calibration, receiver gain error calibration, and antenna feeder system temperature noise error calibration. Furthermore, we present a method for measurements of the calibration error of the oblique path measurement. This results in an oblique path wet delay measurement accuracy of the water vapor radiometer reaching 20 mm (within one month).

Measurement errors in vision based displacement monitoring of masonry bridges

2019 ◽  
Author(s):  
Sinan Acikgoz ◽  
Matthew J. DeJong ◽  
Kenichi Soga
Keyword(s):  
Measurement Errors ◽  
Measurement Accuracy ◽  
Calibration Method ◽  
Textured Surfaces ◽  
Displacement Monitoring ◽  
Camera Model ◽  
Vanishing Points ◽  
Potential Measurement ◽  
Out Of Plane ◽  
The Impact

<p>Vision based displacement monitoring techniques are increasingly used to monitor dynamic displacements in operational bridges. These techniques are particularly well-suited to remotely monitor masonry bridges, which possess textured surfaces that enable effective tracking of sub-mm displacements simultaneously at many locations of the bridge. However, end users need to be aware of potential measurement errors which can impact their measurements. This paper discusses two sources of errors which are particularly relevant for monitoring displacements in masonry bridges with the 2D DIC technique: scaling errors and out of plane movement induced errors. The former category of errors occur due to incorrect scaling of tracking results in pixel units to displacements in metric units. In this paper, a new calibration method is proposed to minimise these errors. The method uses the naturally existing parallel lines in the masonry texture to identify two vanishing points in the image. These vanishing points and the known world coordinates of an identified feature in the image are then used to determine the relative rotation of the image and object planes and the correct scaling factors for different displacement points. The second source of error relates to the limitation of 2D DIC to measure only planar displacements. When out of plane movements occur in the object plane, these are registered incorrectly as in-plane movements. Using a pinhole camera model, the impact of out of plane movements on measurement accuracy are quantified. The results provide insight into how out of plane errors may be minimised or removed in order to achieve a higher measurement accuracy. The findings are explained with the application of the aforementioned techniques to the monitoring of a masonry viaduct.</p>

Articulated Arm Length Calibration for Cantilever Coordinate Measuring Machine

2013 ◽  
Vol 333-335 ◽  
pp. 77-80 ◽  
Author(s):  
Hong Lei Ran ◽  
Shu Gui Liu ◽  
Hai Tao Zhang
Keyword(s):  
Measurement Accuracy ◽  
Small Volume ◽  
Low Cost ◽  
Coordinate Measuring Machine ◽  
Calibration Method ◽  
Measurement Range ◽  
Precision Error ◽  
Large Measurement ◽  
Measuring Machine ◽  
Error Calibration

Cantilever CMM(short for coordinate measuring machine) is non-orthogonal type one with large measurement range, small volume, light weight, low cost, but lower precision. Error calibration and compensation is an important way to improve the measurement accuracy. This paper presents a new calibration method for the length of articulated arm just using the square. Facility requirement is relatively low and it is easy to operate. Comparing with that measured by laser interferometer, this method has a relatively high accuracy, having a certain value in practical measurement.

scholarly journals Intercomparison of two cavity ring-down spectroscopy analyzers for atmospheric <sup>13</sup>CO<sub>2</sub>  ∕ <sup>12</sup>CO<sub>2</sub> measurement

2016 ◽  
Vol 9 (8) ◽  
pp. 3879-3891 ◽  
Author(s):  
Jiaping Pang ◽  
Xuefa Wen ◽  
Xiaomin Sun ◽  
Kuan Huang
Keyword(s):  
Water Vapor ◽  
Co2 Concentration ◽  
Calibration Method ◽  
Vapor Concentration ◽  
Water Vapor Concentration ◽  
Mixing Ratio ◽  
Ambient Conditions ◽  
Significant Linear Correlation ◽  
The Difference ◽  
Water Vapor Mixing Ratio

Abstract. Isotope ratio infrared spectroscopy (IRIS) permits continuous in situ measurement of CO2 isotopic composition under ambient conditions. Previous studies have mainly focused on single IRIS instrument performance; few studies have considered the comparability among different IRIS instruments. In this study, we carried out laboratory and ambient measurements using two Picarro CO2δ13C analyzers (G1101-i and G2201-i (newer version)) and evaluated their performance and comparability. The best precision was 0.08–0.15 ‰ for G1101-i and 0.01–0.04 ‰ for G2201-i. The dependence of δ13C on CO2 concentration was 0.46 ‰ per 100 ppm and 0.09 ‰ per 100 ppm, the instrument drift ranged from 0.92–1.09 ‰ and 0.19–0.37 ‰, and the sensitivity of δ13C to the water vapor mixing ratio was 1.01 ‰ ∕ % H2O and 0.09 ‰ ∕ % H2O for G1101-i and G2201-i, respectively. The accuracy after correction by the two-point mixing ratio gain and offset calibration method ranged from −0.04–0.09 ‰ for G1101-i and −0.13–0.03 ‰ for G2201-i. The sensitivity of δ13C to the water vapor mixing ratio improved from 1.01 ‰ ∕ % H2O before the upgrade of G1101-i (G1101-i-original) to 0.15 ‰ ∕ % H2O after the upgrade of G1101-i (G1101-i-upgraded). Atmospheric δ13C measured by G1101-i and G2201-i captured the rapid changes in atmospheric δ13C signals on hourly to diurnal cycle scales, with a difference of 0.07 ± 0.24 ‰ between G1101-i-original and G2201-i and 0.05 ± 0.30 ‰ between G1101-i-upgraded and G2201-i. A significant linear correlation was observed between the δ13C difference of G1101-i-original and G2201-i and the water vapor concentration, but there was no significant correlation between the δ13C difference of G1101-i-upgraded and G2201-i and the water vapor concentration. The difference in the Keeling intercept values decreased from 1.24 ‰ between G1101-i-original and G2201-i to 0.36 ‰ between G1101-i-upgraded and G2201-i, which indicates the importance of consistency among different IRIS instruments.

scholarly journals Inter-comparison of two cavity ring-down spectroscopy analyzers for atmospheric <sup>13</sup>CO<sub>2</sub> / <sup>12</sup>CO<sub>2</sub> measurement

2016 ◽  
Author(s):  
Jiaping Pang ◽  
Xuefa Wen ◽  
Xiaomin Sun ◽  
Kuan Huang
Keyword(s):  
Water Vapor ◽  
Co2 Concentration ◽  
Calibration Method ◽  
Vapor Concentration ◽  
Mixing Ratio ◽  
Ambient Conditions ◽  
Significant Linear Correlation ◽  
Before And After ◽  
The Difference ◽  
Water Vapor Mixing Ratio

Abstract. The isotope ratio infrared spectroscopy (IRIS) permits in situ and continuous measurements of CO2 isotopic composition under ambient conditions. Previous studies mainly focused on single IRIS instrument performance, few studies have paid attention to the comparability among different IRIS instruments. In this study, we carried out laboratory and ambient measurements of two Picarro CO2 δ13C analyzers (G1101-i and G2201-i), and evaluated their performance and comparability. The best precision were 0.08 ~ 0.15 ‰ and 0.01 ~ 0.04 ‰, the dependence of δ13C on CO2 concentration were 0.46 ‰ per 100 ppm and 0.09 ‰ per 100 ppm, the instrument drift ranged from 0.92 ~ 1.09 ‰ and 0.19 ~ 0.37 ‰. After upgradation of G1101-i, the sensitivity of δ13C on water vapor mixing ratio were 0.15 ‰ / % H2O and 0.13 ‰ / % H2O for the G1101-i and G2201-i, respectively. The accuracy after corrected by the two-point mixing ratio gain and offset calibration method ranged from −0.04 ~ 0.09 ‰ and −0.13 ~ 0.03 ‰ for G1101-i and G2201-i, respectively. Atmospheric δ13C measurements captured the rapidly changing atmospheric δ13C signals, with the difference of 0.07 ± 0.24 ‰ and 0.05 ± 0.30 ‰ between G1101-i upgraded before and after and G2201-i. Before upgradation of G1101-i, a significant linear correlation was observed between the δ13C difference and water vapor concentration, but there is no significant correlation after upgradation of G1101-i. The difference of Keeling intercept values between G1101-i and G2201-i decrease from 1.24 ‰ to 0.36 ‰, which indicate the importance of consistency among different IRIS instruments.

Research on Three-Position Calibration Method for the Installation Error of Inclinometer with Two-Axis Gravity Accelerometer

2014 ◽  
Vol 1030-1032 ◽  
pp. 1237-1241
Author(s):  
Jiang Hong Deng ◽  
Xin Yuan Chen ◽  
Liang Cai Zeng
Keyword(s):  
Output Voltage ◽  
Calibration Method ◽  
Calibration Error ◽  
Error Angle ◽  
Iterative Calculation ◽  
Attitude Angle ◽  
Drilling Tools ◽  
Error Calibration ◽  
Position Calibration

At present,The installation error calibration of gravity accelerometer for the automatic vertical drilling tools is complex and difficult . For this,the paper presents three-position calibration method for the installation error of inclinometer with two-axis gravity accelerometer. The method is based on the equation about actual attitude angle of the inclinometer, installation error angular of two-axis gravity accelerometer and output voltage. The voltage value of the three position is measured, and iterative calculation with MATLAB is used to obtain the installation error angle. The results of simulation prove that this method can meet the requirements of installation error angle calibration of drilling tools , the calibration error is less than 1.5%.

scholarly journals Vibration Error Correction for the FOGs-Based Measurement in a Drilling System Using an Extended Kalman Filter

2021 ◽  
Vol 11 (14) ◽  
pp. 6514
Author(s):  
Lu Wang ◽  
Yuanbiao Hu ◽  
Tao Wang ◽  
Baolin Liu
Keyword(s):  
Kalman Filter ◽  
Extended Kalman Filter ◽  
Measurement Accuracy ◽  
Original Data ◽  
Calibration Method ◽  
Error Model ◽  
Nonlinear Error ◽  
Measurement While Drilling ◽  
Drilling System ◽  
Vibration Error

Fiber-optic gyroscopes (FOGs)-based Measurement While Drilling system (MWD) is a newly developed instrument to survey the borehole trajectory continuously and in real time. However, because of the strong vibration while drilling, the measurement accuracy of FOG-based MWD deteriorates. It is urgent to improve the measurement accuracy while drilling. Therefore, this paper proposes an innovative scheme for the vibration error of the FOG-based MWD. Firstly, the nonlinear error models for the FOGs and ACCs are established. Secondly, a 36-order Extended Kalman Filter (EKF) combined with a calibration method based on 24-position is designed to identify the coefficients in the error model. Moreover, in order to obtain a higher accurate error model, an iterative calibration method has been suggested to suppress calibration residuals. Finally, vibration experiments simulating the drilling vibration in the laboratory is implemented. Compared to the original data, compensated the linear error items, the error of 3D borehole trajectory can only be reduced by a ratio from 10% to 34%. While compensating for the nonlinear error items of the FOG-based MWD, the error of 3D borehole trajectory can be reduced by a ratio from 44.13% to 97.22%. In conclusion, compensation of the nonlinear error of FOG-based MWD could improve the trajectory survey accuracy under vibration.

scholarly journals High-Accuracy Calibration Based on Linearity Adjustment for Eddy Current Displacement Sensor

Sensors ◽  
2018 ◽  
Vol 18 (9) ◽  
pp. 2842 ◽  
Author(s):  
Wei Liu ◽  
Bing Liang ◽  
Zhenyuan Jia ◽  
Di Feng ◽  
Xintong Jiang ◽  
...  
Keyword(s):  
Eddy Current ◽  
Measurement Accuracy ◽  
Characteristic Curve ◽  
Calibration Method ◽  
High Accuracy ◽  
Output Characteristic ◽  
Displacement Sensor ◽  
Support Vector ◽  
Displacement Sensors ◽  
Calibration Accuracy

High precision position control is essential in the process of parts manufacturing and assembling, where eddy current displacement sensors (ECDSs) are widely used owing to the advantages of non-contact sensing, compact volume, and resistance to harsh conditions. To solve the nonlinear characteristics of the sensors, a high-accuracy calibration method based on linearity adjustment is proposed for ECDSs in this paper, which markedly improves the calibration accuracy and then the measurement accuracy. After matching the displacement value and the output voltage of the sensors, firstly, the sensitivity is adjusted according to the specified output range. Then, the weighted support vector adjustment models with the optimal weight of the zero-scale, mid-scale and full-scale are established respectively to cyclically adjust the linearity of the output characteristic curve. Finally, the final linearity adjustment model is obtained, and both the calibration accuracy and precision are verified by the established calibration system. Experimental results show that the linearity of the output characteristic curve of ECDS adjusted by the calibration method reaches over 99.9%, increasing by 1.9–5.0% more than the one of the original. In addition, the measurement accuracy improves from 11–25 μ m to 1–10 μ m in the range of 6mm, which provides a reliable guarantee for high accuracy displacement measurement.

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