Humidity Measurements Research Articles

Raspberry Pi Based Smart Humidifier with Model Prediction

This work is based on Raspberry Pi and implements three main functions, namely temperature and humidity measurement, automatic switching on or off of the humidification module beyond the threshold, and anti-dry burning warning. The temperature and humidity sensor and pressure sensor receive the data and display it in real time on the serial port monitor. After the data is sent to the serial port, the WiFi module can transmit the data to the mobile phone application for remote real-time monitoring and surveillance. When the mobile phone detects insufficient water in the humidifier, it turns on the operation pump and pumps a fixed amount of water into the humidifier. At the same time, the data detected by the sensor is put into the deep learning model, and the predicted data is analysed to achieve the effect of pre-humidification and regulating the balance of environmental parameters.

Thin-core fiber-based Mach-Zehnder interferometer sensor for monitoring temperature, pressure, and humidity

A Mach-Zehnder interferometer (MZI) sensor based on thin-core fiber (TCF) is proposed. Sensitive materials such as polydimethylsiloxane (PDMS) or gelatin are coated on the surfaces of MZIs to achieve temperature, pressure, and humidity measurements. MZI is composed of single mode fiber (SMF), TCF, and multimode fiber (MMF) spliced together to form a “SMF-MMF-TCF-MMF-SMF” structure. The core/cladding diameters of TCF are 3.8 µm and 80 µm respectively. When three types of optical fibers with different core diameters are cascaded together, many cladding modes are excited to form MZI. Firstly, two similar MZI structures were fabricated designated by MZI1 and MZI2. In order to improve the sensitivity and mechanical strength, a layer of PDMS film was coated on the TCF surface of MZI1. Then, a layer of gelatin film is covered on the TCF surface of MZI2. PDMS has the high thermal expansion coefficient, thermal optical coefficient, and elasticity, and gelatin has good humidity sensitivity properties. The experimental results showed that the temperature and pressure sensitivity of MZI1 coated with PDMS reached −340 pm/°C and −14.3 nm/MPa, respectively, while the humidity sensitivity of MZI2 coated with gelatin reached −112.57 pm/% RH. When a fiber Bragg grating is cascaded with the MZI1, the sensor can achieve simultaneous measurement of temperature and pressure, eliminating crosstalk. The proposed sensor has an extremely simple structure and manufacturing method, which only involves the splicing of optical fiber and the coating by the film. In addition, the proposed sensor has a robust structure, good repeatability and stability, and high sensitivity, which has broad application prospects.

Automatic correction of barometric altimeters using additional air temperature and humidity measurements

A GPS module is often combined with an atmospheric pressure sensor in onboard navigation systems. Thanks to this, using appropriate algorithms comparing the results obtained from GPS and from the barometric altimeter, it is possible to obtain much more accurate indications of the height above sea level. The authors analyzed the problem of correcting barometric altimeter errors caused by non-standard pressure and temperature conditions at sea level and the presence of water vapor in the air. The authors proposed methods of correcting the altimeter error using additional temperature and air humidity measurements. They also proposed a simple method for calibrating the altimeter prior to the mission to estimate the difference in pressure above the standard value. The paper discusses the influence of water vapor on the accuracy of the altimeter indications and the conditions for the applicability of the error correction method. The authors initially considered the possibility of using the method based on the concept of virtual temperature. However, this method was rejected because simulation studies showed that it did not give satisfactory results. Simulation tests were carried out in the MATLAB environment to assess the effectiveness of the proposed methods. The test results turned out to be satisfactory. They can be useful when designing low-cost navigation systems using simple sensors made in MEMS technology. The main envisaged application is in autonomous drone navigation systems.

Design and Implementation of Tilted FBG for Concurrent Temperature and Humidity Measurement using Machine Learning

Tilted Fiber Bragg Grating (TFBG) coated with humidity and temperature responsive material is proposed for simultaneous measurement of environmental parameters. Different types of materials are analyzed to optimize the coating material on the grating structure for the measurement of humidity and temperature simultaneously. The optimized coating material is used to fabricate the sensor and experimentally investigated under different humidity and temperature conditions. To further enhance the performance, machine learning algorithms such as Gaussian Progress Regression, Random Forest, K-Nearest Neighbor, AdaBoost, Gradient Boosting algorithm were trained with the spectrum data to estimate the environmental parameters simultaneously. Gradient boosting algorithm best suited for the estimation with better performance metrics of absolute error of 0.6509, RMS of 2.7412 and MAPE of 1.312 for monitoring temperature and humidity simultaneously.

Oral micro-electronic platform for temperature and humidity monitoring

Intraoral theranostics, the integration of diagnostics and therapeutics within the oral cavity, is gaining significant traction. This pioneering approach primarily addresses issues like xerostomia (dry mouth), commonly resulting from cancer treatment, with a specific focus on monitoring temperature and humidity. This paper introduces the innovative Intra-Oral Portable Micro-Electronic (IOPM) fluidic theranostic device platform. It leverages conventional dental spoons by incorporating advanced sensors for precise measurements of oral temperature and humidity. Personalization options include a microfluidic chip and a tooth model, enabling targeted delivery of therapeutic agents to optimize treatment outcomes. The electronic control system simplifies the administration of fluid dosages, intelligently adjusted based on real-time oral cavity temperature and humidity readings. Rigorous experimental evaluations validate the platform’s precision in delivering fluid volumes at predefined intervals. This platform represents a transformative advancement for individuals contending with oral health challenges such as xerostomia (dry mouth). Furthermore, it has the potential to elevate oral healthcare standards by providing advanced diagnostics and tailored therapeutic solutions, benefiting both patients and dental professionals alike.

Limited Role of Absolute Humidity in Intraurban Heat Variability

Abstract Monitoring and understanding the variability of heat within cities is important for urban planning and public health, and the number of studies measuring intraurban temperature variability is growing. Recognizing that the physiological effects of heat depend on humidity as well as temperature, measurement campaigns have included measurements of relative humidity alongside temperature. However, the role the spatial structure in humidity, independent from temperature, plays in intraurban heat variability is unknown. Here we use summer temperature and humidity from networks of stationary sensors in multiple cities in the United States to show spatial variations in the absolute humidity within these cities are weak. This variability in absolute humidity plays an insignificant role in the spatial variability of the heat index and humidity index (humidex), and the spatial variability of the heat metrics is dominated by temperature variability. Thus, results from previous studies that considered only intraurban variability in temperature will carry over to intraurban heat variability. Also, this suggests increases in humidity from green infrastructure interventions designed to reduce temperature will be minimal. In addition, a network of sensors that only measures temperature is sufficient to quantify the spatial variability of heat across these cities when combined with humidity measured at a single location, allowing for lower-cost heat monitoring networks. Significance Statement Monitoring the variability of heat within cities is important for urban planning and public health. While the physiological effects of heat depend on temperature and humidity, it is shown that there are only weak spatial variations in the absolute humidity within nine U.S. cities, and the spatial variability of heat metrics is dominated by temperature variability. This suggests increases in humidity will be minimal resulting from green infrastructure interventions designed to reduce temperature. It also means a network of sensors that only measure temperature is sufficient to quantify the spatial variability of heat across these cities when combined with humidity measured at a single location.

Openings in ventilated Attics

How big should ventilation openings be in ventilated attics? In Denmark, guidelines describe what is sufficient to remove excess moisture penetrating through the ceiling. These guidelines are based on many years of experience. An important parameter is the tightness of the ceiling. With current regulations for the airtightness of buildings, convection through the ceiling is reduced compared to older buildings. Therefore, it is relevant to review these old rules of thumb and maybe revise them. In this two-year study, tests with different sizes of ventilation openings were conducted in a test house with 18 separate ventilated attics and airtight ceilings. One third of the attics were ventilated according to the guidelines, one third’s ventilation was reduced by one third and the last third had 50 % ventilation of the recommendations. Hourly measurements of temperature and relative humidity in the attics were conducted. Rafters in the attics were tested for mould growth. Six different types of insulation systems were used in the attics (with and without a vapour barrier, different insulation materials, and insulation thickness), therefore, the study also includes these differences. Earlier investigations, with full ventilation in all attics, showed no significant hygrothermal differences between them; consequently, it was assumed that the amount of ventilation would be decisive for the hygrothermal performance. This study follows up on this assumption. Results show little differences between the attics, mainly that having a vapour barrier becomes more important with reduced ventilation, and the insulation thickness and thereby U-value is of less importance. Reducing the requirements for ventilation of attics could be relevant, provided that the ceiling is airtight.

Numerical Model and System for Prediction and Reduction of Indoor Infection Risk

Abstract The developed numerical model assesses the risk of a COVID-19 infection in a room based on the measurements of temperature, relative humidity, CO2 and particle concentration, as well as the number of people and occurrences of speech, coughing, and sneezing obtained through a low-cost sensor system. As the model operates faster than real-time, it can dynamically inform the persons in the room or building management system about the predicted risk level. When the infection risk is high, the model can activate an air purifier equipped with filtration and UV-C disinfection. This solution improves energy efficiency by reducing the ventilation intensity required during colder seasons to maintain the same safety level and activating the purifier only when the predicted infection risk surpasses a specified threshold.

Experimental and Numerical Investigation of Mould Growth Risk on Wooden Load-Bearing Structure in Hemp-lime Concrete Facades

The need for reducing the environmental impact of the production of building materials has accelerated the emergence of new types of bio-based façade systems. Some of these systems are claimed to have hygro-thermal properties that eliminate the need for a dedicated air and/or vapour barrier as a part of the façade buildup. This paper presents a risk assessment of moisture-related deterioration of the wooden load-bearing structure in an existing hemp-lime concrete building façade system constructed without a dedicated air or vapour barrier in Aarhus, Denmark. Destructive investigation found no mould on structure. The façade was then modelled in WUFI 2D and calibrated using time series data from field measurements of temperature and relative humidity internally in the construction and in its surroundings. The calibrated WUFI model was used to simulate the annual moisture cycle using different initial conditions and weather data. The simulation output was analysed for the risk of mould growth at the wooden load-bearing structure using the Mould Growth Index. Results indicate that the initial moisture content of materials, the position of the wood structure, and the season of construction completion is important to consider to minimise risk of mould growth in the build-up.

Integrated Room Monitoring and Air Conditioning Efficiency Optimization Using ESP-12E Based Sensors and PID Control Automation: A Comprehensive Approach

This study addresses the critical need for efficient room monitoring and air conditioning systems, particularly in educational settings like the STMIK STIKOM Indonesia campus. The paper introduces a novel approach that combines ESP-12E based sensors with Proportional-Integral-Derivative (PID) control automation to optimize air conditioning efficiency. Utilizing an ESP-12E microcontroller, the study designed and implemented a room monitoring tool equipped with DHT22 and BH1750 sensors for accurate measurement of temperature, humidity, and light intensity. We also explores the integration of a PID control system into an existing air conditioning (AC) unit. The PID controller was fine-tuned to maintain a stable indoor temperature of 25oCelsius, even when subjected to external heat loads, such as ten LED lamps. The effectiveness of this system was quantified through real-time monitoring of temperature, humidity, and energy consumption, both pre- and post-implementation. Results indicated a rapid and stable response from the PID controller, achieving an amplitude of 1 within 0.08 seconds, thereby confirming its successful tuning and adaptability. We found that this study has broader implications for enhancing energy efficiency and creating conducive learning environments. However, it is worth noting that the research was conducted under specific conditions, and further studies could explore its applicability in different settings.

Drying model based on the relative humidity profile of thin-layer tomatoes in an indirect solar dryer

This work defined the development of a model for thin-film drying of tomatoes using an indi-rect solar dryer. Drying experiments were carried out and the drying model was approximated by a simplified model determined by the measurements collected during the experiments, in particular, the measurement of the relative humidity of the tomato during two days of drying coupled with the thermal behaviour of the drying device in free convection. The results show that with good measurements, it is possible to approximate the drying characteristic curve by a linear model with very high statistical performance indicators. The experiments also show that depending on the drying process adopted, the water behaviour of the tomato can change. In addition, the thin-film drying model adopted made it possible to assess the solar drying kinetics of the tomato variety studied. The results obtained finally show that the dryness of the tomato is reached after about 14 hours of drying. The drying temperature reaches an average of 80°C, and the final product water content after the optimal drying time is about 0.40 kg.water/kg.ms on a dry basis. At the end of this study, we concluded that the drying air temperature represents the most important parameter affecting the drying kinetics. The very good agreement between the experimental and numerical results obtained shows that the theoretical model and assumptions used are acceptable, and that our calculation model is reliable.

A review on versatile applications of polyvinyl alcohol thin films, specifically as sensor devices

AbstractPolyvinyl alcohol (PVA) thin films (PVATFs) have recently exhibited different applications in various fields, such as biomedical, optical, and energy storage. One of their outstanding applications has been known as sensor devices for various physical parameters, such as pH, pressure, gas, chemicals, strain, and humidity measurements. In this paper, after a brief review of the PVATFs biomedical, optical, and energy applications, their role as sensors is discussed in more detail. Afterward, the main preparation methods of the PVATFs sensors, for example, spin and dip coating, chemical bath deposition, and electrodeposition are surveyed. Eventually, the characterization methods of the fabricated PVATF sensors, along with their optimization techniques have been presented.Highlights Various applications of polyvinyl alcohol thin films (PVATFs) are presented. One of their main applications as sensor devices is discussed in more detail. PVATF sensors fabrication, characterization, and optimization are surveyed.

Humidity sensor using numerical simulation and electrospun Pd/TEA/PVA on a U-shaped fiber sensor

In this study, we proposed a novel humidity sensor for environmental monitoring and biomedicine applications. The sensing layer of the U-shaped fiber sensor was fabricated by electrospinning. Used COMSOL Multiphysics software simulation to determine the optimal wavelength and transmission loss by finding the best U-shaped fiber radius between 1 and 2 mm. Results showed at 1550 nm, a 1.5 mm radius had better transmission loss. In the humidity experiment, the U-shaped fiber transmission loss significantly increased from 20% to 70% RH. The average change was 0.222 dB/%RH with a sensitivity of 0.004 dB/%RH and linearity of 0.940, indicating good linearity and reproducibility. Furthermore, the electrospun Pd/Triethanolamine (TEA) wire material improved the sensor layer's sensitivity and stability to humidity, enhancing the humidity measurement response.

A Novel Incentive Routing Protocol with Virtual Projection for Mobile Packet Forwarding Nodes in Wireless Sensor Networks

The size of the Packet Forwarding Nodes (PFNs) is becoming very small as the technology advances in Wireless Sensor Networks (WSNs). The node has an additional parameter with low energy levels. The PFNs are distributed in a square cross-sectional area with each node acting as a Sensing Point (SP) that can be used for various kinds of applications like temperature, atmospheric humidity, acoustic, and pressure measurements. The packet is divided into several fragments where each fragment is considered as fixed or variable length. Each of these packets is sent over multiple PFNs toward the data center using PFNs. The selection of PFNs in the path is picked based on the trust level. In the network even special PFNs are placed which are responsible to deliver the packets toward the data center without losing the data during the transmission. The selection of special PFNs is done by computing the meeting probability, remaining energy computation, computation of data weight, and security value computation. The proposed Incentive Routing Protocol with Virtual Projection (IRPVP) method is compared with the conventional approaches concerning the parameters like delay, link count, resource energy, healthy PFNs, non-healthy PFNs, health ratio computation, remaining energy, control to data ratio, and balancing factor. The simulation outcomes show that the performance of the proposed IRPVP algorithm is better than the other conventional algorithms.

Role of WSOCs and pH on Ammonium Nitrate Aerosol Efflorescence: Insights into Secondary Aerosol Formation.

Efflorescence of ammonium nitrate (AN) aerosols significantly impacts atmospheric secondary aerosol formation, climate, and human health. We investigated the effect of representative water-soluble organic compounds (WSOCs) (sucralose (SUC), glycerol (GLY), and citric acid (CA) on AN:WSOC aerosol efflorescence using vacuum Fourier transform infrared spectroscopy. Combining efflorescence relative humidity (ERH) measurements, heterogeneous nucleation rates, and model predictions, we found that aerosol viscosity, correlating with molecular diffusion, effectively predicted ERH variations among the AN:WSOC aerosols. WSOCs with higher viscosity (SUC and CA) hindered efflorescence, while GLY with a lower viscosity showed a minor effect. At a low AN:CA molar ratio (10:1), CA promoted ERH, likely due to CA crystallization. Increasing the droplet pH inhibited AN:CA aerosol efflorescence. In contrast, for AN:SUC and AN:GLY aerosols, efflorescence is pH-insensitive. With the addition of trivial sulfate, AN:SUC droplets exhibited two-stage efflorescence, coinciding with ammonium sulfate and AN efflorescence. Given the atmospheric abundance, the morphology, phase, and mixing state of nitrate aerosols are significant for atmospheric chemistry and physics. Our results suggest that AN:WSOCs aerosols can exist in the amorphous phase in the atmosphere, with efflorescence behavior depending on the aerosol composition, viscosity, pH, and the cation and anion interactions in a complex manner.

Development of a Low-cost IoT-based Remote Sensing Device for Real-time Atmospheric Data Acquisition and Weather Monitoring

The knowledge of basic meteorological parameters is needful in terms of understanding the atmospheric behavior for a given period and consequently also for creating the weather forecast. In this study, an IOT based atmospheric weather data acquisition device is designed to ease and improve on the current measuring technique of acquiring Temperature, Pressure, and Relative Humidity measurement at different altitude levels. This design aims at solving the problem of inadequate atmospheric data by monitoring atmospheric weather conditions using sensors while the microcontroller processes the data collected and relays it to the user. This research was carried out at the University of Uyo, between September 2021 and January, 2023. Taking cognizance of the fact that weather forecasting is of great relevance in our world, this system has been designed using a BME280 module for the atmospheric parameters capturing, an ESP8266 as the microcontroller for Data processing, and a wireless module for processing and transfer of the data from the BME module, a NEO6M GPS module for longitude and latitude, a Li-ion cell to power the components and then a TP4056 circuit to recharge the Li-ion cell. A web server application known as Thingspeak.com was incorporated to help the user interact and access the acquired data to make for ease of understanding and real-time logging of the data obtained. The device successfully transmitted real-time weather data of the target atmospheric parameters captured by it to its users remotely. The results prove that this device is optimally effective and viable for capturing atmospheric parameters for real-time monitoring purposes. This work is relevant in the weather forecasting sector, agricultural sector, as well as to individuals who may have need of gathering information about the atmosphere for proactive planning of daily activities.

Impacts of humidity measurement uncertainties and an uncertainty-tolerant economizer control strategy for air-conditioning systems

Economizer control is a practical and very important measure to achieve energy savings for air-conditioning systems during moderate seasons. The enthalpy-based economizer control approach is appreciated in Hong Kong due to hot-humid climates, but its performance is often affected by sensor uncertainties. Humidity sensors are especially prone to drift out of calibration, their uncertainties are critical and cannot be ignored. This study quantitatively analysed the impacts of humidity measurement uncertainties on enthalpy-based economizer control and found that they may lead to an increase of up to 35.56 % in the total energy consumption of an air handling unit. An uncertainty-tolerant economizer control strategy is proposed to reduce the impacts. The measured relative humidity of fresh air and return air can be corrected online and used to calculate the fresh air and return air enthalpies. The proposed uncertainty-tolerant economizer control strategy has been validated systematically on a virtual platform. The results showed that the average root-mean-square error of the fresh air and return air enthalpies were reduced by 87.92 and 91.39 %, respectively. Compared with the total energy consumption of the air handling unit using conventional control strategy, it was reduced by 1.02–24.58 % when using the uncertainty-tolerant economizer control strategy.

Optical fiber Fabry–Perot sensor based on BPQDs-PVA compound for humidity measurement

A high-sensitivity fiber humidity sensor based on Fabry–Perot interferometer is experimentally proposed. The sensor is fabricated by coating black phosphorus quantum dots (BPQDs)-polyvinyl alcohol (PVA) film on the end face of single mode fiber via controllable dipping method. Benefit from the BPQDs-PVA based cavity, the length and the refractive index of the BPQDs-PVA compound changes with ambient humidity, evidently modulating the interference spectrum. Experimental results show that the sensor achieves a maximum humidity sensitivity of 4.844 nm/%RH in the humidity range of 33%–56%RH with a low temperature cross sensitivity of 0.017%RH °C−1. Meanwhile, stability test exhibits a low instability of 0.016%RH. Together with the advantages of simple manufacture, small size and fast response, the sensor has broad practical application prospect.

Cold Climate Challenges: Analysis of Heat Recovery Efficiency in Ventilation Systems

As building energy consumption gains ever-increasing attention worldwide, the focus on addressing it through the examination and optimization of efficient heat recovery solutions continues to intensify. With well-insulated and airtight buildings, the proportion of heating needs attributed to ventilation is growing, leading to the widespread integration and optimization of heat recovery solutions in mechanical ventilation systems. Heat recovery in ventilation is a highly efficient strategy for reducing heat losses and conserving energy. This study involves the investigation of a ventilation unit installed in an apartment situated in Riga, Latvia, as a practical examination of heat recovery system efficiency within the Latvian climate conditions, representing a cold climate region. The objective of this study was to examine the heat recovery efficiency of the ventilation system in the Latvian climate with variable outdoor and exhaust air parameters, given that the dry heat recovery efficiency is different from the actual heat recovery efficiency. The ventilation unit was equipped with a plate heat exchanger at an airflow rate of 105 m3/h. To evaluate heat recovery efficiency, extensive measurements of air temperature and relative humidity were conducted. The collected data was analyzed, employing statistical regression analysis to ensure measurement reliability and assess correlations. The findings indicated a strong correlation between variables such as heat content, moisture content, and sensible air parameters. It was observed that the actual heat recovery efficiency was 6% higher than the calculated dry efficiency, emphasizing the importance of considering real-world conditions in heat recovery assessments. Additionally, regression analysis demonstrated a positive linear correlation with a coefficient of 0.77, highlighting the dependency between actual measurements and the theoretical model. These quantitative outcomes provide essential insights for optimizing heat recovery systems and enhancing energy-efficient ventilation practices, especially in cold climate environments. Moreover, this study highlights the strong correlation between variables such as heat content, moisture content, and sensible air parameters. Findings offer essential insights for optimizing heat recovery systems and enhancing energy-efficient ventilation practices, especially in cold climate environments.

Field investigation of non-uniform environment in a Venlo-type greenhouse in Yangling, China

Non-uniform environmental conditioning has established substantial energy-saving and conditioning effects in residential buildings, however, few studies on the technology applied in greenhouses have been conducted. Semi-enclosed greenhouse development is hindered by energy consumption. To better apply non-uniform environmental conditioning technology in greenhouses, it is necessary to investigate the non-uniform characteristics of field environment parameters. Therefore, spatial and temporal measurements of indoor temperature and relative humidity in a Venlo-type greenhouse in Yangling, China, were conducted on June 5–11, 2022. Temperature and humidity sensors were arranged in the greenhouse at 4.5 m intervals, in the canopy, cultivation, center, and root areas. Temperature and humidity measurement points on the greenhouse walls were selected. The measurement results showed large fluctuations in the indoor temperature and relative humidity over time. The difference between indoor and outdoor average temperatures ranged from -5–10 °C and temperatures unsuitable for tomato growth were identified, although some passive conditioning methods such as ventilation and water spraying were employed, which indicates the necessity of active heating and cooling. Based on the measured data, the nonuniformity coefficients of temperature and relative humidity in different directions in the greenhouse were calculated. A larger non-uniformity in the vertical direction was found compared to that in the horizontal direction. These results suggest the possibility of non-uniform environmental conditioning. A rough estimation of the energy consumption by the two different condition modes, namely zone-specific and overall conditioning, was made. A huge energy saving of 69.6 % by the zone-specific conditioning mode was revealed compared to the overall conditioning. This implies a huge advantage in energy efficiency by non-unform environmental conditioning technologies applied in greenhouses. The study provides useful data for understanding non-uniform environments in greenhouses and the application of non-uniform environmental conditioning technologies.