High-precision Measurement System Research Articles

High-precision frequency measurement system based on different frequency quantization phase comparison

Aiming at the requirements of phase comparison without frequency normalization, a high-precision frequency measurement system is proposed based on different frequency quantization phase comparison. Using group phase difference pulse in the least common multiple period, the period of frequency standard signal, the period of the measured signal and the pulse width of group phase difference can be respectively counted with the aid of FPGA technology. The obtained counter value is saved and sent to host computer. The measured frequency can be obtained by the data processing of the host computer. Experimental results show that the short-term frequency stability of the system better than E−12/s is achieved. Compared to the traditional frequency measurement system, the system have the advantages of wide measurement range, high frequency stability, low phase noise and low development cost. The system not only plays an important role in precise measurement physics fields such as high-precision transmission and comparison of time and frequency, measurement and suppression of phase noise, but also has a wider application in localization of spatial motion radiation source, satellite navigation equipment, precise time frequency measurement, communication, radar and other high-tech fields.

Highly precise and real-time measurements of 13CO2/12CO2 isotopic ratio in breath using a 2 μm diode laser

Real-time breath gas analysis with high accuracy, precision and time resolution, as a promising, non-invasive, fast and reliable tool, is important in medical diagnostics. Especially stable isotopologues of carbon dioxide is applied to multiple research areas including the diagnosis of gastrointestinal diseases. Helicobacter pylori (H. pylori) is one of the most frequent bacterial infectious diseases in human beings and is now recognized as one of the key risk factors for chronic gastritis, peptic ulcers, stomach cancer and lymphoma. In contrast to traditional invasive tests, the most reliable non-invasive method in the diagnosis of the H. pylori infection is considered to be 13C-urea breath test which is implemented by measuring the 13CO2/12CO2 isotope ratio in human breath. Tunable diode laser absorption spectroscopy (TDLAS) has the advantages of fast response, low drift, good gas selectivity and high detection sensitivity, and it is very convenient to develop a high precision, real-time and online measurement system. A precision laser spectrometer for the measurement of CO2 isotope abundance in human breath (with CO2 concentration of 4%-5%) or high concentration gas is designed and evaluated based on TDLAS technology. The spectrometer contains a novel compact dense-pattern multipass cell with a small volume of 280 cm3 and an effective optical path length of 26. 4 m. The cell is in conjunction with a fiber-coupled distributed feedback diode laser operating at 2.008 μm. Wavelength modulation spectroscopy approach is used. The mass flow, pressure and temperature of the cell are actively controlled, and able to keep long-term stability. The influence of laser power fluctuation is eliminated by fitting the baseline with cubic polynomial to normalize the raw spectrum. Moving window regression is used to remove the influence of frequency drift on measuring isotope abundance. The system measurement precision is improved by wavelet denosing and Kalman filtering. The experimental results demonstrate that moving window regression method not only extends the stability time of the system but also improves the measurement precision of isotope abundance well, the wavelet denoising improves the signal-to-noise ratio by 2 times that by the method of multi-spectral average, the stability time of the system is 100 s given by Allan variance, and the measurement precision of CO2 isotope ratio is 0. 067‰ after Kalman filtering. The use of small multi-pass cell and the default of denoising devices make the system more portable and improve the real-time and online measurement performance of the system. In addition to the measurement of 13CO2/12CO2 isotope ratio in human breath, by replacing different lasers, the spectrometer can also be used to measure trace gas concentration and the stable isotope abundance of many gas molecules in atmosphere. Therefore, the spectrometer will have broad applications in the areas of medical diagnosis, carbon cycle study and environmental monitoring.

Absolute distance measurement based on asymmetric cross-correlation of femtosecond pulse

Optical frequency comb is a kind of new pulse source, whose repetition rate and phase are locked. Optical frequency comb plays an important role in absolute distance measurement and time-frequency metrology. Lots of laser ranging methods such as time-of-flight and multi-heterodyne interferometry based on femtosecond laser pulse have been used in distance measurement. In this paper, a high-precision distance measurement system based on optical sampling by cavity tuning is set up to realize a long absolute distance measurement. And a kind of error compensation method is proposed based on the asymmetric cross-correlation patterns. In traditional optical sampling by cavity tuning measurement system, the fiber link is inserted into the reference path to extend the non-ambiguity distance, which does not have a good performance in arbitrary distance measurement. In our system, we use a 116-meter-long fiber which is inserted into the measuring path to extend the non-ambiguity distance. Besides, dispersion compensation technique is used to control the shape of the laser pulse. An asymmetric optical pulse is used as the light source, so that we can obtain extremely asymmetric cross-correlation patterns. The cross-correlation patterns can be acquired by sweeping the repetition frequency. We use an arbitrary waveform generator to provide the scanning voltage, and the scanning voltage can adjust the repetition rate of the pulse and has a frequency of 1 Hz. There will be two peaks on the envelope of cross-correlation pattern, and both peaks can be used to obtain the distance information. When the laser propagates in vacuum and the system is stabilized, the distance between these two peaks is constant, and we can use this distance to obtain the important factor N, which is used to describe the number of the pulse. As a result, we can realize absolute distance measurement without the help of other measurement systems. However, due to the dispersion of the medium, the distance between these two peaks is not constant, which means that the asymmetry of the cross-correlation patterns in dispersion medium will influence the measurement results. And the deviation is relevant to the peak-to-peak distance. We use the difference among the peak-to-peak distances at different positions to correct the measurement results. A comparison of our results with those from a commercial He-Ne laser interferometer shows that they are in agreement within 2 μm over 50 m distance, corresponding to a relative precision of 1.9×10-7.

Platinum RTD sensor based multi-channel high-precision temperature measurement system for temperature range −100°C to +100°C using single quartic function

A method and system for measuring multiple temperature points using two wire configuration Resistance Temperature Detectors (RTD) for temperature range −100°C to +100°C is mainly composed of the Micro Controller Unit (MCU), analog–digital converter (ADC), reference Voltage source, Multiplexers (MUX) and resistance network including the RTD temperature sensors. The RTDs are sequentially scanned using a reference/constant voltage source, and resistance values of the RTDs are calculated based on the voltage measured across the RTDs and the current sensing resistor. Improving the precision of temperature measurement is based on a line fitting algorithm—Newton’s divided differences interpolation polynomial based on three reference resistor values representing two extreme end points and the center point of the temperature range for which the system is made. The test results show that the device temperature measurement precision can reach ±0.02°C, has the advantage of using a single quartic function for the entire temperature range −100°C to +100°C with dynamic calibration to address errors related to in-circuit resistance, tolerance, temperature coefficient, linearity and offset errors in the circuit, and also supports detection of degradation of linearity and offset in the circuit because of the aging factor.

Wavefront distortion of hypersonic plate boundary layer under two-dimensional strip

Two-dimensional strip is a common flow control method to accelerate flow transition. The wavefront distortion resulting from hypersonic boundary layer has been investigated in virtue of theoretical analysis and wind tunnel experiments. Wavefront measurement system is used to measure the wavefront distortion of hypersonic boundary flow, and compare the distribution of flow wavefront with and without strip. The results prove that high-precision wavefront measurement system can present not only wavefront but also density distribution before the flow transition of boundary layer. In addition, the experimental results show that the wavefront distortion increases quickly when the flow is obviously unstable. Finally, comparing the distribution of wavefront induced by strip with the corresponding data without strip, we find that the mean wavefront, root mean square and peak-valley value of wavefront with strip are much larger than that without strip.

The Effect of Tailoring Morphology of Ni-Rich Cathode Oxides on Electrochemical Stability for Lithium Ion Batteries

Understanding the correlation between physical and electrochemical/chemical properties are significantly crucial for development of electrode materials for lithium ion batteries. Among the materials, Ni-rich cathode materials with high energy density has degradation issue of electrochemical performance due to the parasitic reaction at the cathode electrolyte interface. The core-shell or concentration gradient materials consisting of a high-Ni core and a relatively high-Mn outer layer might be potential candidate providing improved stability as well as cycle life performance. In this respect, the porosity of final sintered particle can be an indicator to affect the electrode stability. The strategy to tune the particle porosity is introduced by controlling a feed rate of reactants during co-precipitation synthesis. The structural characteristics was compared for the materials obtained by different feed rate X-ray diffraction, electron microscopy, electrochemical performances, particle size distribution and porosity. The interfacial kinetic reaction between the Ni-rich cathode and a nonaqueous electrolyte at different SOCs is investigated by our home-built high-precision leakage current measurement system. This study can be an indicator for the safety of Ni-rich cathode by co-precipitation.

Conditioning Safety Index of Ni-Rich Cathode Oxides for Lithium Ion Batteries

Ni-rich cathode materials with high energy density has degradation issue of electrochemical performance due to the significant side reaction between electrolyte and cathode. To solve this, a Full Concentration Gradient (FCG) materials consisting of a high-Ni core and a relatively high-Mn outer layer was designed to provide improved stability as well as cycle life characteristic. However, a Ni-rich core still has some possibilities to be contact with electrolyte, especially if the particle in the core part is unexpectedly porous. We found the strategy to tune the particle porosity by controlling a feed rate of transition metal sulfate solutions and ammonium hydroxide solution during co-precipitation synthesis using Continuous Stirred Tank Reactor (CSTR). Additionally, the effect of surfactant was studied in the standpoint of the electrode stability. The structural characteristics was compared for the materials obtained by different feed rate with analysis of by X-ray diffraction, electron microscopy and dynamic light scattering. The interfacial kinetic reaction between the delithiated Ni-rich cathode and a nonaqueous electrolyte was investigated by our home-built high-precision leakage current measurement system. The result of this study indicated a different reaction phenomenon and further implies that the safety of Ni-rich cathode by co-precipitation could be controlled.

Revisiting the Corrosion of the Aluminum Current Collector in Lithium-Ion Batteries.

The corrosion of aluminum current collectors and the oxidation of solvents at a relatively high potential have been widely investigated with an aim to stabilize the electrochemical performance of lithium-ion batteries using such components. The corrosion behavior of aluminum current collectors was revisited using a home-build high-precision electrochemical measurement system, and the impact of electrolyte components and the surface protection layer on aluminum foil was systematically studied. The electrochemical results showed that the corrosion of aluminum foil was triggered by the electrochemical oxidation of solvent molecules, like ethylene carbonate, at a relative high potential. The organic radical cations generated from the electrochemical oxidation are energetically unstable and readily undergo a deprotonation reaction that generates protons and promotes the dissolution of Al3+ from the aluminum foil. This new reaction mechanism can also shed light on the dissolution of transitional metal at high potentials.

Study of High Precision Measurement System in Pulsed Laser Ranging

To improve the accuracy of time interval measurement in pulsed laser ranging system, a method which combines clock counting and differential delay line based on Field Programmable Gate Array (FPGA) is used in time interval measurement. FPGA sets up two delay lines in its internal, one of them consists of several buffers; another consists of several D flip-flops. The time delay between them serves as the smallest unit of time interval measurement, which is the step length of measuring time interval within half a clock cycle. Compared with clock counting method, this method put time interval measurement accuracy up to ten times. The experiment results show that time interval of system measurement reach at ±300 ps, and 3 cm measuring distance precision is achieved, which means that the method can satisfy the requirements of high precision ranging.

Influence of pellet seating on the external ballistic parameters of spring-piston air guns.

In firearm examiners' and forensic specialists' casework as well as in air gun proof testing, reliable measurement of the weapon's muzzle velocity is indispensable. While there are standardized and generally accepted procedures for testing the performance of air guns, the method of seating the diabolo pellets deeper into the breech of break barrel spring-piston air guns has not found its way into standardized test procedures. The influence of pellet seating on the external ballistic parameters was investigated using ten different break barrel spring-piston air guns. Test shots were performed with the diabolo pellets seated 2mm deeper into the breech using a pellet seater. The results were then compared to reference shots with conventionally loaded diabolo pellets. Projectile velocity was measured with a high-precision redundant ballistic speed measurement system. In eight out of ten weapons, the muzzle energy increased significantly when the pellet seater was used. The average increase in kinetic energy was 31% (range 9-96%). To conclude, seating the pellet even slightly deeper into the breech of spring-piston air guns might significantly alter the muzzle energy. Therefore, it is strongly recommended that this effect is taken into account when accurate and reliable measurements of air gun muzzle velocity are necessary.

Automated simultaneous measurement of the δ(13) C and δ(2) H values of methane and the δ(13) C and δ(18) O values of carbon dioxide in flask air samples using a new multi cryo-trap/gas chromatography/isotope ratio mass spectrometry system.

The isotopic composition of greenhouse gases helps to constrain global budgets and to study sink and source processes. We present a new system for high-precision stable isotope measurements of carbon, hydrogen and oxygen in atmospheric methane and carbon dioxide. The design is intended for analyzing flask air samples from existing sampling programs without the need for extra sample air for methane analysis. CO2 and CH4 isotopes are measured simultaneously using two isotope ratio mass spectrometers, one for the analysis of δ(13) C and δ(18) O values and the second one for δ(2) H values. The inlet carousel delivers air from 16 sample positions (glass flasks 1-5 L and high-pressure cylinders). Three 10-port valves take aliquots from the sample stream. CH4 from 100-mL air aliquots is preconcentrated in 0.8-mL sample loops using a new cryo-trap system. A precisely calibrated working reference air is used in parallel with the sample according to the Principle of Identical Treatment. It takes about 36 hours for a fully calibrated analysis of a complete carousel including extractions of four working reference and one quality control reference air. Long-term precision values, as obtained from the quality control reference gas since 2012, account for 0.04 ‰ (δ(13) C values of CO2 ), 0.07 ‰ (δ(18) O values of CO2 ), 0.11 ‰ (δ(13) C values of CH4 ) and 1.0 ‰ (δ(2) H values of CH4 ). Within a single day, the system exhibits a typical methane δ(13) C standard deviation (1σ) of 0.06 ‰ for 10 repeated measurements. The system has been in routine operation at the MPI-BGC since 2012. Consistency of the data and compatibility with results from other laboratories at a high precision level are of utmost importance. A high sample throughput and reliability of operation are important achievements of the presented system to cope with the large number of air samples to be analyzed. Copyright © 2016 John Wiley & Sons, Ltd.

Vibration Measurement in High Precision for Flexible Structure Based on Microscopic Vision

Vibration measurement for flexible structures is widely used in various kinds of precision engineering fields. However, it is a challenge to measure vibration in special applications, such as cryogenic, dangerous and magnetic interference. In this paper, a high-precision vibration measurement system based on machine vision is designed. The circle center on the target is employed as the image feature. The circle feature is extracted using the improved algorithm based on gradient Hough transform. Then the image Jacobian matrix is used to compute the vibrations in Cartesian space from the image feature changes. Experiments verify the effectiveness of the proposed methods.

High-Dynamic and High-Precise Optical Current Measurement System Based on the Faraday Effect

In this paper, a high-dynamic and high-precise optical current measurement system based on the Faraday effect is presented. First, the sensor concept is presented and different sensor constructions are analyzed. Then, a measurement system based on a rare-earth iron garnet film is investigated. The measurement system uses multiple signal processing channels to increase the signal-to-noise ratio. Furthermore, the measurement range exceeds a rotation of 180° and therefore requires a counting mechanism to count the number of rotations. Finally, the precision of the presented system is analyzed. The precision is determined to be 4.9 ppm at a rotation range of 3300°.

A reservoir trap for antiprotons

We have developed techniques to extract arbitrary fractions of antiprotons from an accumulated reservoir, and to inject them into a Penning-trap system for high-precision measurements. In our trap-system antiproton storage times >1.08 years are estimated. The device is fail-safe against power-cuts of up to 10h. This makes our planned comparisons of the fundamental properties of protons and antiprotons independent from accelerator cycles, and will enable us to perform experiments during long accelerator shutdown periods when background magnetic noise is low. The demonstrated scheme has the potential to be applied in many other precision Penning trap experiments dealing with exotic particles.

Large-scale compact range on-site alignment based on laser tracker measurement network

Large-scale compact range generally consists of multi reflectors, how to align these numerous small reflectors into a high precision surface, this has to be carefully taken into account following two key issues: measurement system and alignment approach. Firstly, aim to solve the large scale, high precision and longtime stability measurement system issues, a measurement network based on laser tracker metrology was established, key technology for the metrology including: deducing the error in point measurement and uncertainty ellipsoid of laser tracker; optimizing the measuring stations and carrying out weighted measurement network regression. Secondly, a practical alignment approach was proposed; this approach divides the entire process into three key phases including: marked points positioning phase, gaps equalizing phase and constrained surfaces smoothing phase; due to gradually improve the adjustment precision step-by-step, it effectively reduces the adjustment iterations and avoids mutual physical contact, and ensure the surface accuracy and the gaps widths. Finally, the on-site alignment of a large compact range with a width of 23m and height of 16m which will generate a Φ15m quiet zone at 40Ghz is presented; The uncertainty of the measurement network is controlled to 0.025mm, and the final surface root mean square accuracy was up to 0.054mm and the gaps widths achieved 0.4±0.2mm.

S1360102 板ばねを利用した研磨による月面反射鏡の平滑加工技術の開発

A high precision measurement system of the distance between the moon and earth is under development by the National astronomical observatory of Japan, in which the round-trip time of laser from the earth to the moon is measured to calculate the distance. In the system, a new lunar laser reflector (LLR) placed on the moon is necessary to measure the round-trip time, but has not yet been realized. In this study, we proposed a new polishing method using a plate spring suitable for polishing the LLR to realize it. To evaluate our proposed method, we polished single crystal Si wafers as workpieces, and examined surface roughness and machined shapes of the polished areas. As a result, surface roughness after the polishing was better than that before polishing. This proves that our proposed method using the plate spring enables the smoothing of surfaces. However, the machined areas were not shaped to flat, but to be curved. The reason for this is possibly due to the non-uniformity of the polishing load. Thus, the flatness of the machined areas should be improved in future study.

Research on high-precision hole measurement based on robot vision method

A high-precision vision detection and measurement system using mobile robot is established for the industry field detection of motorcycle frame hole and its diameter measurement. The robot path planning method is researched, and the non-contact measurement method with high precision based on visual digital image edge extraction and hole spatial circle fitting is presented. The Canny operator is used to extract the edge of captured image, the Lagrange interpolation algorithm is utilized to determine the missing image edge points and calculate the centroid, and the least squares fitting method is adopted to fit the image edge points. Experimental results show that the system can be used for the high-precision real-time measurement of hole on motorcycle frame. The absolute standard deviation of the proposed method is 0.026 7 mm. The proposed method can not only improve the measurement speed and precision, but also reduce the measurement error.

Design of High Precision Temperature Sensor Based on Platinum Resistance

for Pt100 platinum resistance temperature measurement system has low accuracy, duplicate hardware circuit design and other issues, the articles design a high-precision temperature measurement system with Pt100 platinum resistance. With Pt100 temperature sensor, article takes STM32F103 as the control center through filtering, amplification and other signal conditioning circuit and a method of combining software look-up table to compensate the nonlinear compensation, thus achieving high-precision temperature measurement. Research results show that the system has a measurement accuracy high stability, scalability, and other characteristics.

Use of Thirty-Meter Laser Interference Comparator for Metrological Assurance in the Oil and Gas Industry

The metrological characteristics of modern high-precision laser measurement systems and instruments for the measurement of the level of petroleum and petroleum products used in commercial accounting are presented. Results of studies of the components of the nonexcluded systematic and random errors, the standard deviation, and confidence limits of the total error of the transmission of the unit of length by a 30-m laser interference comparator incorporated into the structure of the state primary standard of the unit of length, the meter, are presented.

Defocusing rectified multi-frequency patterns for high-precision 3D measurement

The sinuousness of the projected fringe patterns has a great influence on the accuracy of structured light-based 3D measurement. In this paper, a defocusing rectified multi-frequency patterns (DRMP) method is presented to eliminate the effect caused by the projector. The cause of phase error is derived and analyzed to prove the non-necessity of gamma correction in the DRMP method. First, the multi-frequency binary codes are projected onto the measured object, and a Gaussian smoothing filter is adopted to defocus the distorted fringe images captured by the imaging system. Then, an optimized phase unwrapping path which has the smallest phase error is proposed to obtain the unwrapped phase. After that, the stereo rectification and the two-step matching methods are applied to obtain the corresponding matching lines and points, respectively. Finally, we demonstrate that the proposed method can be implemented into the high-precision 3D shape measurement system. The validation experiments show that the proposed method is more precise and efficient compared with previous methods.