scholarly journals Self-Referenced Multifrequency Phase-Resolved Luminescence Spectroscopy

Sensors ◽  
2020 ◽  
Vol 20 (19) ◽  
pp. 5482
Author(s):  
Angel de la Torre ◽  
Santiago Medina-Rodríguez ◽  
Jose C. Segura ◽  
Jorge F. Fernández-Sánchez
Keyword(s):  
Chemical Sensors ◽  
Modulation Frequency ◽  
Measuring System ◽  
Luminescence Lifetime ◽  
Luminescence Spectroscopy ◽  
Theoretical Formulation ◽  
Analog To Digital ◽  
Excitation Signal ◽  
Emission Signal ◽  
The Difference

Phase-resolved luminescence chemical sensors provide the analyte determination based on the estimation of the luminescence lifetime. The lifetime is estimated from an analysis of the amplitudes and/or phases of the excitation and emission signals at one or several modulation frequencies. This requires recording both the excitation signal (used to modulate the light source) and the emission signal (obtained from an optical transducer illuminated by the luminescent sensing phase). The excitation signal is conventionally used as reference, in order to obtain the modulation factor (the ratio between the emission and the excitation amplitudes) and/or the phase shift (the difference between the emission and the excitation phases) at each modulation frequency, which are used to estimate the luminescence lifetime. In this manuscript, we propose a new method providing the luminescence lifetimes (based either on amplitudes or phases) using only the emission signal (i.e., omitting the excitation signal in the procedure). We demonstrate that the luminescence lifetime can be derived from the emission signal when it contains at least two harmonics, because in this case the amplitude and phase of one of the harmonics can be used as reference. We present the theoretical formulation as well as an example of application to an oxygen measuring system. The proposed self-referenced lifetime estimation provides two practical advantages for luminescence chemical sensors. On one hand, it simplifies the instrument architecture, since only one analog-to-digital converter (for the emission signal) is necessary. On the other hand, the self-referenced estimation of the lifetime improves the robustness against degradation of the sensing phase or variations in the optical coupling, which reduces the recalibration requirements when the lifetimes are based on amplitudes.

scholarly journals Axial Error of Spindle Measurements Using a High-Frequency-Modulated Interferometer

Crystals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 801
Author(s):  
Thanh-Trung Nguyen ◽  
Thanh-Tung Vu ◽  
Thanh-Dong Nguyen ◽  
Toan-Thang Vu
Keyword(s):  
High Precision ◽  
Modulation Frequency ◽  
Zeeman Effect ◽  
Machining Process ◽  
Measuring System ◽  
Laser Source ◽  
Small Displacement ◽  
Interference Signal ◽  
High Modulation ◽  
The Difference

In this paper, a novel, compact, and high-precision axial error measurement using a frequency-modulated interferometer is developed. Normally, heterodyne interferometers are a powerful system for small displacement measurements due to their property of being less sensitive to temperature and pressure variations. However, the maximum measurement speed of the heterodyne interferometer is around 5 m/s because it is usually limited by the difference in frequency between the two components of the laser beam, which is no larger than 3 MHz or 20 MHz corresponding laser source based on the Zeeman effect and acousto-optic modulator, respectively. The proposed measuring system is realized by modulating the frequency of the laser diode source at a high modulation frequency and using lock-in amplifiers to extract the harmonics of the interference signal. The measurement speed is proportional to the modulation frequency. Thus, the higher the modulation frequency, the higher the measuring speed attains. The frequency-modulated interferometer is then applied to measure the axial error of an ultra-precision spindle. The proposed system can be a capable solution for noncontact and high-precision spindle error measurements in the machining process.

Generalized Heterodyne Configurations for Photo-induced Force Microscopy

2019 ◽  
Author(s):  
Le Wang ◽  
Devon Jakob ◽  
Haomin Wang ◽  
Alexis Apostolos ◽  
Marcos M. Pires ◽  
...  
Keyword(s):  
Spatial Resolution ◽  
Repetition Rate ◽  
Modulation Frequency ◽  
High Harmonic ◽  
Chemical Imaging ◽  
Heterodyne Detection ◽  
Force Microscopy ◽  
Wide Range ◽  
The Difference ◽  
Afm Cantilever

<div>Infrared chemical microscopy through mechanical probing of light-matter interactions by atomic force microscopy (AFM) bypasses the diffraction limit. One increasingly popular technique is photo-induced force microscopy (PiFM), which utilizes the mechanical heterodyne signal detection between cantilever mechanical resonant oscillations and the photo induced force from light-matter interaction. So far, photo induced force microscopy has been operated in only one heterodyne configuration. In this article, we generalize heterodyne configurations of photoinduced force microscopy by introducing two new schemes: harmonic heterodyne detection and sequential heterodyne detection. In harmonic heterodyne detection, the laser repetition rate matches integer fractions of the difference between the two mechanical resonant modes of the AFM cantilever. The high harmonic of the beating from the photothermal expansion mixes with the AFM cantilever oscillation to provide PiFM signal. In sequential heterodyne detection, the combination of the repetition rate of laser pulses and polarization modulation frequency matches the difference between two AFM mechanical modes, leading to detectable PiFM signals. These two generalized heterodyne configurations for photo induced force microscopy deliver new avenues for chemical imaging and broadband spectroscopy at ~10 nm spatial resolution. They are suitable for a wide range of heterogeneous materials across various disciplines: from structured polymer film, polaritonic boron nitride materials, to isolated bacterial peptidoglycan cell walls. The generalized heterodyne configurations introduce flexibility for the implementation of PiFM and related tapping mode AFM-IR, and provide possibilities for additional modulation channel in PiFM for targeted signal extraction with nanoscale spatial resolution.</div>

Study of Wireless Torque Measurement System Based on CC2500

2011 ◽  
Vol 383-390 ◽  
pp. 5300-5303
Author(s):  
Wei Liu ◽  
Xiao Jie Song ◽  
Wen Gang Chen
Keyword(s):  
Signal To Noise Ratio ◽  
Digital Data ◽  
Measuring System ◽  
Instrumentation Amplifier ◽  
Torque Sensor ◽  
Torque Measurement ◽  
Analog To Digital ◽  
Wireless Transceiver ◽  
Precision Measuring ◽  
Transmission Shaft

It’s very difficult to get high precision measuring result using contact torquemeter because of very low signal-to-noise ratio. To overcome this defect, a wireless torque measuring system is designed based on CC2500. This system uses strain gauge torque sensor to measure the surface principal stress of the transmission shaft, and get the maximum shearing stress, and then the torque that the transmission shaft bears. The weak output signal of torque sensor is magnified by the instrumentation amplifier AD623, and sent to the analog-to-digital convertor. These digital data are transmited to the portable receiving terminal by the wireless transceiver chip CC2500. The dynamic wireless torque measurement is realized by this system.

PHOTOMETER-LINKED MICROCOMPUTER SYSTEM ENABLES PRECISE CHROMOGENIC PROTHROMBIN TIME ASSAYS

1987 ◽  
Author(s):  
U Siekmann ◽  
D Dittrih ◽  
R E Zimmermann
Keyword(s):  
Research Work ◽  
Laboratory Diagnosis ◽  
Measuring System ◽  
Microcomputer System ◽  
Analog To Digital ◽  
Chromogenic Assay ◽  
Photometric Assay ◽  
Double Beam ◽  
Total Absorbance ◽  
Absorbance Data

In coagulation diagnostics photometric assay procedures are in widespread use. Due to the availability of new specific chromogenic peptide substrates, automated instruments play an important role in clinical routine laboratory diagnosis. For research work, the benefit of expensive industrial photometric coagulation systems is questionable, especially as the program cannot be adapted by the user. For this purpose we developed an inexpensive microcomputer-controlled measuring system as well as a suitable photometric assay which allows to determine chromogenic clotting times with any conventional spectrophotometer.Absorbance data were taken from the analog chart-recorder output of a double-beam spectrophotometer, digitized by a 12 bit analog-to-digital converter and read by the computer via an interface. Menu driven, user orientated / user dialogue based compiled BASIC software was written to enable data acquisition and processing.During the chromogenic assay procedure, automatically collected absorbance data were displayed, stored, analyzed immediately, saved on disk for later kinetic analysis and printed.Preliminary results with our chromogenic PT-assay indicate excellent reproducabi1ity of the test. The clotting time itself is defined as the interval from the beginning of the test to the moment when a preselected absorbance change occurred. Standard curves can automatically be calculated by regression routines after measurement of reference values.It must be emphasized that the occurence of fibrinogen-generated turbidity during the chromogenic assay sometimes influences the total absorbance significantly. For this reason the reaction time has to be limited by a low optical endpoint setting.

Effect of Reinforcement on Flexural Properties of Brittle Composites

2013 ◽  
Vol 747 ◽  
pp. 76-79
Author(s):  
Md. Zakaria Hossain
Keyword(s):  
Flexural Modulus ◽  
Flexural Properties ◽  
Experiment Data ◽  
Third Order ◽  
Theoretical Formulation ◽  
Ductile Materials ◽  
The Difference ◽  
Brittle Layers ◽  
Brittle Composites ◽  
Section Analysis

The flexural properties in terms of ductility of laminated brittle composites have been studied experimentally in the laboratory. Test specimens consisting of variable layers of mesh were prepared and tested under third point loadings. It was observed that the brittle matrix altered it properties and behaved as the ductile matrix even with small amount of ductile materials. The causes of the change in the properties have been clarified by analyzing the experiment data. The experimental results were verified by the theoretical formulation. The formulation showed that the flexural modulus of the entire section of brittle composites obtained by section analysis is equal to the modulus of ductile layers plus a factor of the difference of modulus of ductile and brittle layers. This factor is third order of ductile layer causing flexural properties in brittle composite even with 10% of ductile materials.

Research of Electrochemistry Measuring System Based on Saliva Glucose

2011 ◽  
Vol 301-303 ◽  
pp. 1139-1144
Author(s):  
Li Ying Jiang ◽  
Li Jie Ren ◽  
Qing Hua Chen ◽  
Guang Zhao Cui
Keyword(s):  
Glucose Oxidase ◽  
Chemical Sensors ◽  
Linear Relation ◽  
Glucose Solution ◽  
Solution Concentration ◽  
Measuring System ◽  
Cross Linking ◽  
Glucose Content ◽  
Relationship Of ◽  
The Relationship

According to the relationship of glucose content in diabetes saliva and blood, the biosensor for detecting saliva glucose was introduced based on electrochemical detecting principle, glucose oxidase was immobilized onto the surface of electrode by glutaraldehyde cross-linking. The measuring system was designed by using potentiostat for amperometric chemical sensors. The characters of the microsystem has been demonstrated with the detection of standard glucose solution concentration of saliva parameter. Compared with the data obtained from the instrument CHI660A, it showed that has a good linear relation in the linear range of 0-2200µmol/L, with the correlation coefficient of 0.9531.

Comparison of luminous intensity distributions

2016 ◽  
Vol 49 (1) ◽  
pp. 62-83 ◽  
Author(s):  
F Gassmann ◽  
U Krueger ◽  
T Bergen ◽  
F Schmidt
Keyword(s):  
Structural Properties ◽  
Light Source ◽  
Radiation Characteristic ◽  
Luminous Flux ◽  
Luminous Intensity ◽  
Measuring System ◽  
Operating Parameters ◽  
Data Noise ◽  
Flux Data ◽  
The Difference

Luminous intensity distributions enable an evaluation of the spatial radiation characteristic of a light source. This radiation characteristic is determined by the structural properties of the light source, its operating parameters and the properties of the measuring system. This paper describes some possible methods and rules for comparing luminous intensity distributions. The focus is on the development of calculation rules for quantifying the differences between two luminous intensity distributions. The difference measures developed allow the user to establish an objective comparison between luminous intensity distributions, this comparison being completely independent of the measuring system, the properties of the luminous intensity distributions and the users themselves. Further, the dependence of the properties of luminous intensity distributions resulting from measurement practice, such as adjustment uncertainties, regions that cannot be covered or measured, deviations of the total luminous flux, data noise and resolution differences, are discussed, and appropriate pre-processing and correction steps proposed. In addition, various visualisations of the differences between two luminous intensity distributions are demonstrated and the functionality of the difference measures developed is documented.

scholarly journals Electro-acustic influence of the measuring system on the photoacoustic signal amplitude and phase in frequency domain

2016 ◽  
Vol 14 (1) ◽  
pp. 9-20 ◽  
Author(s):  
Sanja Aleksic ◽  
Dragana Markushev ◽  
Dragan Pantic ◽  
Mihajlo Rabasovic ◽  
Dragan Markushev ◽  
...  
Keyword(s):  
Frequency Domain ◽  
Flicker Noise ◽  
Modulation Frequency ◽  
Signal Amplitude ◽  
Photoacoustic Signal ◽  
Measuring System ◽  
Coherent Noise ◽  
Characteristic Frequencies ◽  
Signal Distortions ◽  
Set Up

The paper discusses the most common impacts of the measuring system on the amplitude and phase of the photoacoustic signals in the frequency domain using the open-cell experimental set-up. The highest signal distortions are detected at the ends of the observed modulation frequency range from 20 Hz to 20 kHz. The attenuation of the signal is observed at lower frequencies, caused by the electronic filtering of the microphone and sound card, with characteristic frequencies of 15 Hz and 25 Hz. At higher frequencies, the dominant signal distortions are caused by the microphone acoustic filtering, having characteristic frequencies around 9 kHz and 15 kHz. It has been found that the microphone incoherent noise, the so called flicker noise, is negligibly small in comparison to the signal and does not affect the signal shape. However, a coherent noise originating from the power modulation system of the light source significantly affects the shape of the signal in the range greater than 10 kHz. The effects of the coherent noise and measuring system influence are eliminated completely using the relevant signal correction procedure targeting the photoacoustic signal generated by the sample.

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