Analog-to-digital angular displacement converter with error compensation

The operating principle of a new analog-to-digital angular displacement converter circuit that makes it possible to reduce the error of the phase shifter is considered. __________ Translated from Izmeritel’naya Tekhnika, No. 8, pp. 31–33, August, 2007.     

Instrumental resistance-frequency converter chip

A special-purpose analog integrated circuit chip is described that converts the ratio between the temperature transducer resistance to a certain reference resistance into repetition period of pulses of fixed duration. The chip includes circuits for resistance current and current-oscillation period converters, and a current pulse generator in the power supply section. Stability of converter parameters is ensured by using supplies with temperature-stabilized current drift.Translated from Izmeritel'naya Tekhnika, No. 11, pp. 52–54, November, 1994.     

Methodic error of conversion of analog signals into frequency-modulated pulse signals

Conclusions For an equiprobable distribution of the position of the beginning of interval T_i on the time axis, _m manifests itself as an uncorrelated random error.If the pulse duration is negligible in comparison with the time interval between adjacent pulses, the ME of the error _m is equal to zero for AFC's with uniform or nonuniform pulse sequences.The RMSD of the error _m varies with T_i, assuming a number of extremum values [_m]_max. For the same values of T_i andf, [_mn]_max exceeds [_mu]_max by a factor of not more than 2. If the maximum allowable values of the RMSD of the methodic error _m are assigned on the basis of experimental conditions, the minimum allowable measurement time of the secondary instrument which receives the AFC signal can be found by means of (7) and (11).Translated from Izmeritel'naya Tekhnika, No. 12, pp. 53–55, December, 1972.     

Mechanical angular displacement converter

Conclusion Equations have been derived for estimating and calculating the main parameters of a mechanical converter of angular displacement; the maximum accuracy attainable with a device of this type of an angular displacement of rotating masses has been determined. This converter can be used in systems where an angular error of the order of 0.1 is permissible.Translated from Izmeritel'naya Tekhnika, No. 8, pp. 45–46, July, 1970.     

Instrumental error in chromotomosynthetic hyperspectral imaging

Chromotomosynthetic imaging (CTI) is a method of convolving spatial and spectral information that can be reconstructed into a hyperspectral image cube using the same transforms employed in medical tomosynthesis. A direct vision prism instrument operating in the visible (400-725?nm) with 0.6?mrad instantaneous field of view (IFOV) and 0.6-10?nm spectral resolution has been constructed and characterized. Reconstruction of hyperspectral data cubes requires an estimation of the instrument component properties that define the forward transform. We analyze the systematic instrumental error in collected projection data resulting from prism spectral dispersion, prism alignment, detector array position, and prism rotation angle. The shifting and broadening of both the spectral lineshape function and the spatial point spread function in the reconstructed hyperspectral imagery is compared with experimental results for monochromatic point sources. The shorter wavelength (λ<500 nm) region where the prism has the highest spectral dispersion suffers mostly from degradation of spectral resolution in the presence of systematic error, while longer wavelengths (λ>600 nm) suffer mostly from a shift of the spectral peaks. The quality of the reconstructed hyperspectral imagery is most sensitive to the misalignment of the prism rotation mount. With less than 1° total angular error in the two axes of freedom, spectral resolution was degraded by as much as a factor of 2 in the blue spectral region. For larger errors than this, spectral peaks begin to split into bimodal distributions, and spatial point response functions are reconstructed in rings with radii proportional to wavelength and spatial resolution.     

Intelligent four-channel frequency–code converter

The structural flowchart of an intelligent four-channel frequency–code converter, its functions, and its technical characteristics are considered. A self-diagnostics algorithm is proposed.     

Software-configurable converter for sensor signals

A new approach to the organization of software for sensor signal converters is considered. A solution to the problem using an operational system and modelling within that system is proposed.     

Correlation of RF signals during angular compounding

A theoretical analysis of the correlation between radio-frequency (RF) echo signal data acquired from the same location but at different angles is presented. The accuracy of the theoretical results is verified with computer simulations. Refinements to previous analyses of the correlation of RF signals originating from the same spatial location at different angular positions are made. We extend the analysis to study correlation of RF signals coming from different spatial locations and eventually correlation of RF signal segments that intersect at the same spatial location. The theory predicts a faster decorrelation with a change in the insonification angle for longer RF echo signal segments. As the RF signal segment becomes shorter, the decorrelation rate with angle is slower and approaches the limit corresponding to the correlation of RF signals originating from the same spatial location. Theoretical results provide a clear understanding of angular compounding techniques used to improve the signal-to-noise ratio in ultrasonic parametric imaging and in elastography.     

微弱裂纹信号的稀疏编码提取

针对重大技术装备中关键基础部件早期裂纹信号提取困难这一问题,提出一种基于独立分量分析（ICA）的稀疏编码收缩（SCS）去噪方法,即采用泛化高斯模型（GGM）在ICA空间中估计信号独立系数的概率密度函数（PDF）,并利用最大后验（MAP）估计方法进行非线性去噪的微弱信号提取方法。通过对不同信噪比的含噪微弱裂纹信号的提取研究,结果表明,此方法能提取出输入信噪比低于-27dB的微弱信号,且波形与频谱均能较好的和原信号保持一致。同时,其去噪效果远远好于小波降噪方法,是一种较好的微弱信号提取方法。     

A method of error reduction in reading angular quantities

Translated from Izmeritel'naya Tekhnika, No. 4, pp. 10–12, April, 1992.     

Measurement converter for sensor signals in modular systems

We consider a factility for measurement of signals from different types of sensors; the system complies with the CAMAC and VME standards, and it is designed to increase measurement accuracy. We present the basic characteristics of the system. Translated from Izmeritel'naya Tekhnika, No. 11, pp. 15–17, November, 1997.