Pressure sensor chip utilizing electrical circuit of piezosensitive differential amplifier with negative feedback loop (PDA-NFL) for 5 kPa

High sensitive (S = 11.2 ± 1.8 mV/V/kPa with nonlinearity error 2KNL = 0.15 ± 0.09%/FS) small-sized (4.00x4.00 mm2) silicon pressure sensor chip utilizing new electrical circuit for microelectromechanical systems (MEMS) in the form of differential amplifier with negative feedback loop (PDA-NFL) for 5 kPa differential was developed. The advantages are demonstrated in the array of output characteristics, which prove the relevance of the presented development, relative to modern developments of pressure sensors with Wheatstone bridge electrical circuit for 5 kPa range.

Calculation of the components of the temperature measurement error by a resistance thermocouple of an installed unbalanced bridge

The article has devoted to solving an urgent problem related to the determination and calculation of the components of the temperature measurement error. A grain drying machine had selected as the object of research, in which the temperature of the grain at the exit from the machine is measured with the help of a Cu50 resistance thermocouple installed in an unbalanced bridge. It had found that the scale of the measuring device, calibrated in degrees Celsius, will have a nonlinearity error, which increases towards the end of the measurement range. For the Cu50 resistance thermocouple installed in the grain drying machine, when measuring the temperature in the range of 0 … 100 °C in absolute terms, the nonlinearity error was 0.3 mA, in relative terms - 4.4 %, which is quite large. The measurement error has calculated with a tolerance for the nominal resistance of the thermistor ± 0.1 Ohm, which in the given form was 0.5%. The resulting value indicates that this component will have an insignificant effect on the total measurement error. The measurement error due to the supply voltage drop by 0.2 V in relative form was 4.2 %. Thus, the voltage drops when using an unbalanced bridge will have a significant effect on the measurement result.

Design and Optimization of a Linear Wavenumber Spectrometer with Cylindrical Optics for Line Scanning Optical Coherence Tomography

We report the design of a high-efficiency spectral-domain spectrometer with cylindrical optics for line scanning optical coherence tomography (OCT). The spectral nonlinearity in k space (wavenumber) lowers the depth-dependent signal sensitivity of the spectrometers. For linearizing, in this design, grating and prism have been introduced. For line scanning, a cylindrical mirror is utilized in the scanning part. Line scanning improves the speed of imaging compared to fly-spot scanning. Line scanning OCT requires a spectrometer that utilizes cylindrical optics. In this work, an optical design of a linear wavenumber spectrometer with cylindrical optics is introduced. While there are many works using grating and prism to linearize the K space spectrometer design, there is no work on linearizing the k-space spectrometer with cylindrical optics for line scanning that provides high sensitivity and high-speed imaging without the need for resampling. The design of the spectrometer was achieved through MATLAB and ZEMAX simulations. The spectrometer design is optimized for the broadband light source with a center wavelength of 830 ± 100 nm (8.607 μm−1− 6.756 μm−1 in k-space). The variation in the output angle with respect to the wavenumber can be mentioned as a nonlinearity error. From our design results, it is observed that the nonlinearity error reduced from 147.0115 to 0.0149 Δθ*μm within the wavenumber range considered. The use of the proposed reflective optics for focusing reduces the chromatic aberration and increases image quality (measured by the Strehl ratio (SR)). The complete system will provide clinicians a powerful tool for real-time diagnosis, treatment, and guidance in surgery with high image quality for in-vivo applications.

Mixed-mode Method Used for Pt100 Static Transfer Function Linearization

Pt100 is a resistance temperature detector characterized by a relatively linear resistance/temperature relationship in a narrow temperature range. However, the Pt100 sensor shows a certain degree of static transfer function nonlinearity of 4.42 % in the range between −200 °C and 850 °C, which is unacceptable for some applications. As a solution to this problem, a mixed-mode linearization method based on a special dual-stage piecewise linear ADC design is proposed in this paper. The first stage of the proposed dual-stage piecewise linear ADC is performed with a low-complex and low-power flash ADC of a novel sequential design. The novelty of the proposed sequential design is reflected in the fact that the number of employed comparators is equal to the flash ADC resolution. The second stage is performed with a delta-sigma ADC with a differential input and differential reference. Using the 6-bit flash ADC of novel design and the 24-bit delta-sigma ADC, the nonlinearity error is reduced to 2.6·10−3 %, in the range between −200 °C and 850 °C. Two more ranges are examined, and the following results are obtained: in the range between 0 °C and 500 °C, the nonlinearity error is reduced from 1.99 % to 5·10−4 %, while in the range between −50 °C and 150 °C, the nonlinearity error is reduced from 0.755 % to 2.15·10−4 %.

Simultaneous Time-Varying Vibration and Nonlinearity Compensation for One-Period Triangular-FMCW Lidar Signal

Frequency modulation continuous wave (FMCW) Lidar inevitably suffers from vibration and nonlinear frequency modulation, which influences the ranging and imaging results. In this paper, we analyze the impact of vibration error coupled with nonlinearity error on ranging for FMCW Lidar, and propose a purely theoretical approach that simultaneously compensates for time-varying vibration and nonlinearity in one-period triangular FMCW (T-FMCW) signals. We first extract the localized characteristics of dechirp signals in time-frequency domain by using a second-order synchro-squeezing transform (second-order SST), and establish an instantaneous ranging model based on second-order SST which can characterize the local distributions of time-varying errors. Second, we estimate the nonlinearity error by using time-frequency information of an auxiliary channel and then preliminarily eliminate the error from the instantaneous measurement range. Finally, we construct a particle filtering (PF) model for T-FMCW using the instantaneous ranging model to compensate for the time-varying vibration error and the residual nonlinearity error, and calculate the range of target by using triangular symmetry relations of T-FMCW. Experimental tests prove that the proposed method can accurately estimate the range of target by compensating for the time-varying vibration and the nonlinearity errors simultaneously in one-period T-FMCW signal.

Analysis and research of methods of linearization of the transfer function of precision semiconductor temperature sensors

The analysis of the nonlinearity of the transfer function of primary temperature transducers based on transistor structures has been performed. It’s shown that the quadratic component of the transfer function creates a significant nonlinearity error up to 0,2-0,6°C. We have developed methods of linearization based on both the formation of compensatory measuring current and change of the conversion factor of the output scaling amplifier at certain ranges of temperature measurement, which ensure their use in precision temperature measuring devices. The measurement error does not exceed 0.01°C in the range of 30-100°C.

Investigation on the Differential Quadrature Fabry–Pérot Interferometer with Variable Measurement Mirrors

Due to the common path structure being insensitive to the environmental disturbances, relevant Fabry–Pérot interferometers have been presented for displacement measurement. However, the discontinuous signal distribution exists in the conventional Fabry–Pérot interferometer. Although a polarized Fabry–Pérot interferometer with low finesse was subsequently proposed, the signal processing is complicated, and the nonlinearity error of sub-micrometer order occurs in this signal. Therefore, a differential quadrature Fabry–Pérot interferometer has been proposed for the first time. In this measurement system, the nonlinearity error can be improved effectively, and the DC offset during the measurement procedure can be eliminated. Furthermore, the proposed system also features rapid and convenient replacing the measurement mirrors to meet the inspection requirement in various measuring ranges. In the comparison result between the commercial and self-developed Fabry–Pérot interferometer, it reveals that the maximum standard deviation is less than 0.120 μm in the whole measuring range of 600 mm. According to these results, the developed differential Fabry–Pérot interferometer is feasible for precise displacement measurement.

Effect of nasal airway nonlinearities on oscillometric resistance measurements in infants

Oscillometric measurements of respiratory system resistance (Rrs) in infants are usually made via the nasal pathways, which not only significantly contribute to overall Rrs but also introduce marked flow acceleration-dependent distortions. Here, we propose a method for correcting flow acceleration-dependent nonlinearity error based on in vitro measurements in 3D-printed upper airway casts of infants as well as in vivo measurements. This correction can be adapted to estimate Rrs from a single intrabreath oscillometric measurement.

Seismic Discrimination between Earthquakes and Explosions Using Support Vector Machine

The discrimination between earthquakes and explosions is a serious issue in seismic signal analysis. This paper proposes a seismic discrimination method using support vector machine (SVM), wherein the amplitudes of the P-wave and the S-wave of the seismic signals are selected as feature vectors. Furthermore, to improve the seismic discrimination performance using a heterodyne laser interferometer for seismic wave detection, the Hough transform is applied as a compensation method for the periodic nonlinearity error caused by the frequency-mixing in the laser interferometric seismometer. In the testing procedure, different kernel functions of SVM are used to discriminate between earthquakes and explosions. The outstanding performance of a laser interferometer and Hough transform method for precision seismic measurement and nonlinearity error compensation is confirmed through some experiments using a linear vibration stage. In addition, the effectiveness of the proposed discrimination method using a heterodyne laser interferometer is verified through a receiver operating characteristic curve and other performance indices obtained from practical experiments.