Portable Measurement Research Articles

Wireless-based portable device heart rate measurement as biomedical devices for stress detection

Stress can increase the heart rate, causing dangerous conditions that cause significant harm and even death. Therefore, managing stress well to control the heart rate is vital. Monitoring stress levels using biomedical devices is essential to prevent further damage to the individual. Regular monitoring facilitates the acquisition of individual stress levels through heart rate information. In this research, a MAX30100 sensor can produce Beats Per Minute (BPM) data, which show the stress experienced by a person during four daily activities (sitting, walking, running, and sleeping) and when watching a horror movie. This research underscores the potential of cost-effective wireless solutions to increase portability and facilitate real-time monitoring and remote surveillance. The researchers introduced an innovative methodology by reusing everyday consumer devices, initially intended for routine activities, to measure stress levels in a unique context—precisely in a controlled experiment involving a movie-watching scenario. The ultimate achievement of this research was creating a stationary heart rate monitoring device that is easy to access, easy to use, space-saving, and adept at effectively tracking stress indicators. BPM readings obtained from the MAX30100 sensor have scores similar to those obtained from the heart rate app. The researchers proposed the inclusion of other sensors, such as a photoplethysmograph, an electrocardiogram, and galvanic skin response, to provide a more holistic assessment of stress. Leveraging cloud technology for data storage enables long-term monitoring and in-depth analysis of stress patterns over time.

Investigating the Congestion Levels on a Mesoscopic Scale During Outdoor Events

In event management, preventing excessive overcrowding is not only essential for providing comfort but also crucial for ensuring safety. However, understanding the crowd dynamics of participants in outdoor events can be challenging. One of the primary reasons is the limited availability of sensing systems suitable for outdoor use. Challenges include the need for power outlets and adapting to dynamic environmental conditions and unclear event boundaries. Consequently, there is still uncertainty about which measurements can be conducted to scientifically manage crowding based on sound principles. Therefore, there is a need for systems that are capable of discerning spatial and temporal heterogeneity in density and accurately estimating the number of people in regions of interest in both sparse and congested areas. In this study, we propose a novel approach for measuring and understanding crowd states at outdoor events. We designed a highly portable measurement system utilizing Bluetooth technology to monitor crowd density in real time, ensuring uninterrupted data collection even in remote event locations. This system stands out for its ability to operate effectively under diverse weather and lighting conditions without power outlets, making it highly adaptable to various outdoor settings. In our experiments, conducted at four distinct outdoor event locations, we used a 360° camera and LiDARs to validate the system. For instance, we deployed the system at 40-m intervals in a shopping district during a high-density parade. This deployment enabled us to capture the movement of the crowd and estimate the total number of people within the district. A key finding was the system’s capability to detect temporal and spatial congestion in both sparse and crowded areas. The system’s potential to estimate crowd sizes and manage diverse outdoor events marks an advancement over traditional methods like cameras and LiDARs.

Error Analysis of Normal Surface Measurements Based on Multiple Laser Displacement Sensors.

The robotic drilling of assembly holes is a crucial process in aerospace manufacturing, in which measuring the normal of the workpiece surface is a key step to guide the robot to the correct pose and guarantee the perpendicularity of the hole axis. Multiple laser displacement sensors can be used to satisfy the portable and in-site measurement requirements, but there is still a lack of accurate analysis and layout design. In this paper, a simplified parametric method is proposed for multi-sensor normal measurement devices with a symmetrical layout, using three parameters: the sensor number, the laser beam slant angle, and the laser spot distribution radius. A normal measurement error distribution simulation method considering the random sensor errors is proposed. The measurement error distribution laws at different sensor numbers, the laser beam slant angle, and the laser spot distribution radius are revealed as a pyramid-like region. The influential factors on normal measurement accuracy, such as sensor accuracy, quantity and installation position, are analyzed by a simulation and verified experimentally on a five-axis precision machine tool. The results show that increasing the laser beam slant angle and laser spot distribution radius significantly reduces the normal measurement errors. With the laser beam slant angle ≥15° and the laser spot distribution radius ≥19 mm, the normal measurement error falls below 0.05°, ensuring normal accuracy in robotic drilling.

Design Aspects for Portable LED-Based Colorimetric Characterisation Systems Targeting Liquid Analytes.

Colorimetric characterisation systems based on LEDs and RBG sensors are straightforward to implement, are highly integrable allowing for portable measurement systems and can be constructed using widespread and affordable components. They have already proved to be a satisfactory solution in several applications related to chemical analysis. In this paper, we present an RGB sensor-based prototype for colorimetric characterisation, which can accommodate cuvettes with optical paths of 10 mm and 40 mm. We assessed the impact of experimental condition parameters such as the variability of the analyte volume in the cuvette, as well as the presence of floating particles or deposits at the bottom of the cuvette. While these would not impact the result given by a spectrophotometer that generally has a directional light source, they must be considered in LED/RGB sensor analysers in which the light path is not tightly controlled. We demonstrated that there is a minimal sensor height above the bottom of the cuvette and a minimal analyte level (both depending on the prototype optical path length) above which the analyte volume and the presence of floating particles and deposits have no impact on the prototype output signal. Finally, based on these results, we proposed a test method for a quick dye-displacement assay, in which the reagent is a dye-loaded molecularly imprinted polymer that is poured directly into a cuvette.

Electrochemical DNA-based sensors for measuring cell-generated forces

Mechanical forces play an important role in cellular communication and signaling. We developed in this study novel electrochemical DNA-based force sensors for measuring cell-generated adhesion forces. Two types of DNA probes, i.e., tension gauge tether and DNA hairpin, were constructed on the surface of a smartphone-based electrochemical device to detect piconewton-scale cellular forces at tunable levels. Upon experiencing cellular tension, the unfolding of DNA probes induces the separation of redox reporters from the surface of the electrode, which results in detectable electrochemical signals. Using integrin-mediated cell adhesion as an example, our results indicated that these electrochemical sensors can be used for highly sensitive, robust, simple, and portable measurements of cell-generated forces.

Lateral and temporal constraints on the depositional history of the Bonneville Salt Flats, Utah, USA

AbstractThe depositional history of the Bonneville Salt Flats, a perennial saline pan in Utah's Bonneville basin, has poor temporal constraints, and the climatic and geomorphic conditions that led to saline pan formation there are poorly understood. We explore the late Pleistocene to Holocene depositional record of Bonneville Salt Flats cores. Our data challenge the assumption that the saline pan formed from the desiccation of Lake Bonneville, the largest late Pleistocene lake in the Great Basin, which covered this area from 30 to 13 cal ka BP. We test two hypotheses: whether climatic transitions from (1) wet to arid or (2) arid to wet led to saline pan deposition. We describe the depositional record with radiocarbon dating, sedimentological structures, mineralogy, diatom, ostracode, and portable X-ray fluorescence spectrometer measurements. Gypsum and carbonate strontium isotope ratio measurements reflect changes in water sources. Three shallow saline lake to desiccation cycles occurred from >45 and >28 cal ka BP. Deflation removed Lake Bonneville sediments between 13 and 8.3 cal ka BP. Gypsum deposition spanned 8.3 to 5.4 cal ka BP, while the oldest halite interval formed from 5.4 to 3.5 cal ka BP during a wetter period. These findings offer valuable insights for sedimentologists, archaeologists, geomorphologists, and land managers.

Initial observations of the impacts of infauna on portable free fall penetrometer measurements in sandy parts of Mobile Bay

The seabed surface provides habitat for abundant and diverse fauna, whose burrowing activities have been shown to modify geotechnical properties of surface sediments. Whether these impacts affect geotechnical properties on larger scales of traditional measurements has not been well studied. This study represents an initial attempt to assess whether infaunal activity affects seabed properties on a scale relevant for, and therefore, detectable in portable free fall penetrometer measurements. Specifically, we examine sediment strength profiles of the upper 10–70 cm of sandy (poorly graded sand and muddy sand) seabed sediments in Mobile Bay, Alabama, USA, hypothesizing that infauna create heterogeneity in sediment structure that would lead to variability in PFFP vertical profiles as well as among replicate measurements at a site. Sediments were composed predominantly of sands, with only 17% of the sites featuring sand contents < 97% and median grain sizes ranging from 0.0987 to 0.3457 mm. Sediment strength generally decreased with a decreasing sand content, but variability was not explained by sand content alone. PFFP impacts in sandier sites (> 97% sand) were limited to the surface few cm, but considerable vertical and spatial variability in muddy sands and lower strength at sites with abundant burrowing infauna suggest that infaunal activities may affect PFFP measurements in these sediments.

Cost-effective layered double hydroxides/conductive polymer nanocomposites for electrochemical detection of wastewater pollutants

There is an urgent need to develop multifunctional cost-effective nanomaterials and nanocomposites that can be used in numerous applications while showing high efficiency and cheaper implementation compared to conventional techniques and/or materials. In this work, zinc/iron layered double hydroxide (LDH) and polyaniline (PANI) were synthesized as a model LDH/conductive polymer nanocomposite, which is a promising family of cheap multifunctional materials. This electrochemical properties of this nanocomposite was investigated for detection of heavy metal (HM) ions in water streams, using lead as a model HM. In the present work, zinc/iron LDH and PANI was assigned as carbon paste electrode modifier. The composite was fully characterized using various characterization techniques including X-ray diffraction (XRD), scanning electron microscope (SEM), and Fourier transform InfraRed (FTIR). The electrochemical redox reactions of lead (II) ions at the modified electrode interface were investigated using cyclic voltammetry (CV), differential pulse voltammetry (DPV), Accordingly, a linear relation of Pb2+ ions was achieved in the concentration range 1–80 µM with limit of detection (LOD) was 167.8 nM and limit of quantification (LOQ) was 559.4 nM. Furthermore, the cost of using such material for lead removal using a typical adsorption study was compared to using conventional inductively coupled plasma (ICP) or atomic absorption spectrometry (AAS) equipment for tracking HM removal during the adsorption process. Cost analysis revealed that the final overall cost of the modified carbon paste electrode is estimated as 1.25 USD. This cost represents less than 0.1% of the total cost required to conduct the same adsorption study using a typical ICP or AAS equipment. This composite can pave the road towards portable measurements for onsite detection of wastewater pollutants using cheap disposable-electrodes as compared to massive expensive off site equipment such as ICP and AAS.

Design of a portable electrochemical impedance spectroscopy measurement system based on AD5941 for lithium-ion batteries

Electrochemical impedance spectroscopy (EIS) is an important indicator of state of health (SOH) for Lithium-ion batteries (LIBs), but its measurement relies mainly on electrochemical workstations that are costly and cannot be used for on-site testing. This paper designs a portable EIS measurement system based on the high-precision impedance converter chip AD5941, which utilizes a wide-frequency constant current source as the excitation signal and detects the LIB's response voltage signal to obtain EIS data ranging from 0.1 Hz to 2 kHz. In addition, a software interface based on LabVIEW is developed for real-time graphically displaying the EIS information. EIS measurement experiments are performed on a NCR-18650B LIB at different charge states in both single-frequency mode and frequency-sweep mode using the newly-designed EIS measurement system. The results show that in single-frequency mode, the impedance measurement error at 1 kHz is below 2.8 % compared with a standard single-frequency electrochemical impedance analyzer. In frequency-sweep mode, the Nyquist plot of the LIB is obtained at different charge states and exhibits good repeatability. Moreover, an effective equivalent circuit analysis of the EIS data was performed, which further substantiates the practical utility of the EIS system in providing valuable insights into the battery's electrochemical behavior. Compared to the traditional EIS measurement systems, the proposed EIS measurement system has the advantages of low cost, easy operation and portability, which exhibits promising prospects for on-site EIS applications.

Pre-processing techniques using a machine learning approach to improve model accuracy in estimating oil palm leaf chlorophyll from portable chlorophyll meter measurement

Chlorophyll is essential for plants because it absorbs and adjusts solar energy as an energy source in photosynthesis. Thus, chlorophyll content can be used as an indicator of plant performance. However, laboratory analysis should usually be conducted to measure chlorophyll content, which requires a lot of tools and time. Therefore, Chlorophyll Meter SPAD (Soil Plant Analysis Development) is a portable tool to estimate relative leaf chlorophyll rapidly. Still, it needs to be modeled and validated to get accurate results as laboratory analysis. Therefore, appropriate data pre-processing techniques are required before entering the model development stage. The pre-processing techniques included data collection, identification, and anomalies check. In addition, a machine-learning method was employed to do K-Means clustering during checking data anomalies. The results showed that the pre-processing stages increased the R-value from 0.588 to 0.912 and reduced the Mean Absolute Percentage Error (MAPE) value from 58.91% to 39.86%.

Relating Geotechnical Sediment Properties and Low Frequency CHIRP Sonar Measurements

Low frequency acoustic methods are a common tool for seabed stratigraphy mapping. Due to the efficiency in seabed mapping compared to geotechnical methods, estimating geotechnical sediment properties from acoustic surveying is attractive for many applications. In this study, co-located geotechnical and geoacoustic measurements of different seabed sediment types in shallow water environments (&lt;5 m of water depth) are analyzed. Acoustic impedance estimated from sediment properties based on laboratory testing of physical samples is compared to acoustic impedance deduced from CHIRP sonar measurements using an inversion approach. Portable free fall penetrometer measurements provided in situ sediment strength. The results show that acoustic impedance values deduced from acoustic data through inversion fall within a range of ±25% of acoustic impedance estimated from porosity and bulk density. The acoustic measurements reflect variations in shallow sediment properties such as porosity and bulk density (~10 cm below seabed surface), even for very soft sediments (su &lt; 3 kPa) and loose sands (~20% relative density). This is a step towards validating the ability of acoustic methods to capture geotechnical properties in the topmost seabed layers.

A Comparison of Critical Speed and Critical Power in Runners Using Stryd Running Power.

Although running traditionally relies on critical speed (CS) as an indicator of critical intensity, portable inertial measurement units offer a potential solution for estimating running mechanical power to assess critical power (CP) in runners. The purpose of this study was to determine whether CS and CP differ when assessed using the Stryd device, a portable inertial measurement unit, and if 2 running bouts are sufficient to determine CS and CP. On an outdoor running track, 10 trained runners (V˙O2max, 59.0 [4.2]mL·kg-1·min-1) performed 3 running time trials (TT) between 1200 and 4400m on separate days. CS and CP were derived from 2-parameter hyperbolic speed-time and power-time models, respectively, using 2 (CS2TT and CP2TT) and 3 (CS3TT and CP3TT) TTs. Subsequently, runners performed constant-intensity running for 800m at their calculated CS3TT and CP3TT. Running at the calculated CS3TT speed (3.88 [0.44]m·s-1) elicited an average Stryd running power (271 [28]W) not different from the calculated CP3TT (270 [28]; P = .940; d = 0.02), with excellent agreement between the 2 values (intraclass correlation coefficient = .980). The CS2TT (3.97 [0.42]m·s-1) was not higher than CS3TT (3.89 [0.44]m·s-1; P = .178; d = 0.46); however, CP2TT (278 [29] W) was greater than CP3TT (P = .041; d = 0.75). The running intensities at CS and CP were similar, supporting the use of running power (Stryd) as a metric of aerobic fitness and exercise prescription, and 2 trials provided a reasonable, albeit higher, estimate of CS and CP.

Research on Portable Noncontact COD Measurement Instrument Based on Laser Spectroscopy

Research on Portable Noncontact COD Measurement Instrument Based on Laser Spectroscopy

Effect of body orientation and joint movement on local bioimpedance measurements.

The purpose of this pilot study was to determine if body orientation, skin treatment, joint angle, and shoulder arch movements affect localized bioimpedance spectroscopy (BIS) measurement. Nowadays, there are various wearable and portable impedance measurement tools in different shapes and sizes. Therefore, the body position and orientation of the subject during measurement may be of great importance for the comparability of the results. Ultrasound machine was used to measure the thickness of the skin layers and then bioimpedance measurements were performed for ten young men (age=23 ± 5) at room temperature (22°C) for different body orientations, skin treatments, joint angle, and shoulder arch movements. The results were analyzed using statistical methods and graphical presentation using Python and MatLab. Our observations indicate that there is a significant difference between standing straight up, supine and sitting positions. The results show that there is a significant difference between the two skin treatments (alcohol vs tape stripping). Moreover, joint angle and shoulder arch movements also have an impact on the impedance data. Therefore, to be able to control these factors can potentially improve the quality and comparability of the measured impedance data.

Development of portable dynamic torque power measurement system

Development of portable dynamic torque power measurement system

HRV and EEG correlates of well-being using ultra-short, portable, and low-cost measurements.

Wearable electroencephalography (EEG) and electrocardiography (ECG) devices may offer a non-invasive, user-friendly, and cost-effective approach for assessing well-being (WB) in real-world settings. However, challenges remain in dealing with signal artifacts (such as environmental noise and movements) and identifying robust biomarkers. We evaluated the feasibility of using portable hardware to identify potential EEG and heart-rate variability (HRV) correlates of WB. We collected simultaneous ultrashort (2-min) EEG and ECG data from 60 individuals in real-world settings using a wrist ECG electrode connected to a 4-channel wearable EEG headset. These data were processed, assessed for signal quality, and analyzed using the open-source EEGLAB BrainBeats plugin to extract several theory-driven metrics as potential correlates of WB. Namely, the individual alpha frequency (IAF), frontal and posterior alpha asymmetry, and signal entropy for EEG. SDNN, the low/high frequency (LF/HF) ratio, the Poincaré SD1/SD2 ratio, and signal entropy for HRV. We assessed potential associations between these features and the main WB dimensions (hedonic, eudaimonic, global, physical, and social) implementing a pairwise correlation approach, robust Spearman's correlations, and corrections for multiple comparisons. Only eight files showed poor signal quality and were excluded from the analysis. Eudaimonic (psychological) WB was positively correlated with SDNN and the LF/HF ratio. EEG posterior alpha asymmetry was positively correlated with Physical WB (i.e., sleep and pain levels). No relationships were found with the other metrics, or between EEG and HRV metrics. These physiological metrics enable a quick, objective assessment of well-being in real-world settings using scalable, user-friendly tools.

Development of portable dynamic torque power measurement system

Development of portable dynamic torque power measurement system

Urine osmolality assessment through the integration of urea hydrolysis and impedance measurement.

We present the development and validation of an impedance-based urine osmometer for accurate and portable measurement of urine osmolality. The urine osmolality of a urine sample can be estimated by determining the concentrations of the conductive solutes and urea, which make up approximately 94% of the urine composition. Our method utilizes impedance measurements to determine the conductive solutes and urea after hydrolysis with urease enzyme. We built an impedance model using sodium chloride (NaCl) and urea at various known concentrations. In this work, we validated the accuracy of the impedance-based urine osmometer by developing a proof-of-concept first prototype and an integrated urine dipstick second prototype, where both prototypes exhibit an average accuracy of 95.5 ± 2.4% and 89.9 ± 9.1%, respectively in comparison to a clinical freezing point osmometer in the hospital laboratory. While the integrated dipstick design exhibited a slightly lower accuracy than the first prototype, it eliminated the need for pre-mixing or manual pipetting. Impedance calibration curves for conductive and non-conductive solutes consistently yielded results for NaCl but underscored challenges in achieving uniform urease enzyme coating on the dipstick. We also investigated the impact of storing urine at room temperature for 24 hours, demonstrating negligible differences in osmolality values. Overall, our impedance-based urine osmometer presents a promising tool for point-of-care urine osmolality measurements, addressing the demand for a portable, accurate, and user-friendly device with potential applications in clinical and home settings.

Integration of complementary split-ring resonators into digital microfluidics for manipulation and direct sensing of droplet composition.

This paper demonstrates the integration of complementary split-ring resonators (CSSRs) with digital microfluidics (DMF) sample manipulation for passive, on-chip radio-frequency (RF) sensing. Integration is accomplished by having the DMF and the RF-sensing components share the same ground plane: by designing the RF-resonant openings directly into the ground plane of a DMF device, both droplet motion and sensing are achieved, adding a new on-board detection mode for use in DMF. The system was modelled to determine basic features and to balance various factors that need to be optimized to maintain both functionalities (DMF-enabled droplet movement and RF detection) on the same chip. Simulated and experimental results show good agreement. Using a portable measurement setup, the integrated CSSR sensor was used to effectively identify a series of DMF-generated drops of ethanol-water mixtures of different compositions by measuring the resonant frequency of the CSSR. In addition, we show that a binary solvent system (ethanol/water mixtures) results in consistent changes in the measured spectrum in response to changes in concentration, indicating that the sensor can distinguish not only between pure solvents from each other, but also between mixtures of varied compositions. We anticipate that this system can be refined further to enable additional applications and detection modes for DMF systems and other portable sensing platforms alike. This proof-of-principle study demonstrates that the integrated DMF-CSSR sensor provides a new platform for monitoring and characterization of liquids with high sensitivity and low consumption of materials, and opens the way for new and exciting applications of RF sensing in microfluidics.

Sziklai Pair based Small signal Amplifier with bjt-mosfet Hybrid Unit at 180nm Technology

Two circuit models of Small Signal amplifier, constituted with BJT-MOSFET hybrid unit under Sziklai pair topology are designed and analyzed using ‘PSpice’ and ‘Cadence Virtuoso and Spectre simulation tool (at GPDK 180nm technology)’ respectively. First amplifier (Circuit-1) uses PSpice user-defined model of BJT and MOSFET whereas the second amplifier (Circuit-2) consists of transistors available at GPDK 180nm technology. Circuit-1 can amplify the AC signals of 1mV-1nV range with optimum voltage gain 389.532, 137.570 current gain, 14.464MHz bandwidth and 2.43% THD. However, Circuit-2 can amplify AC signals of 0.1mV-10nV range with 164.018 voltage gain, 32.775 current gain, 11.906 MHz bandwidth, and 13.608E-6% THD. Both the proposed amplifier circuits remove narrow band problem and generate better results than earlier announced small signal Sziklai pair amplifier with BJT-MOSFET hybrid unit in respect of voltage and current gains, bandwidth, THD, and power consumption. Proposed amplifiers successfully address the problem of poor frequency response of small signal Darlington pair amplifier in higher frequency range and narrow bandwidth limitations of small-signal PNP Sziklai pair amplifier. Dependency of the proposed amplifiers at various biasing resistances and performance with temperature variation, noise variation, DC supply variation, and phase variation are also discussed herein. Proposed Circuits display strong dependency over ideal maximum forward beta ‘β’ of NPN transistor, Transconductance ‘VTO’ of P-MOS transistor and additional biasing resistances ‘RA’. Layout of Circuit-2 is found to cover 96.3898µm2 area with 11.32µm length and 8.515µm breadth. Minor percentage variation between pre-layout and post-layout simulation results of Circuit-2 validates the proposed design at GPDK 180nm technology. Monte Carlo and Process Corner analysis are also performed to test the robustness and insensitivity of Circuit-2 against mean value of the parameters and process and mismatch respectively. Performance summary of the proposed circuits and comparison with the recently reported designs shows effectiveness of the proposed circuits in terms of power gain, THD, voltage gain, current gain, input referred noise and power gain. Qualitative analysis of the proposed Circuits recommends its usability as Low Noise Amplifier in the portable RF noise measurement system.