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To establish an accurate and sensitive method to characterize the moisture content of a particular environment.

This paper proposes a relatively simple humidity sensor design consisting of electrodes on a suitable substrate coated with a polyimide material. The changes in relative humidity are denoted by a corresponding change in the polyimide material's electrical resistance profile. The design proposed in this work can be microfabricated and integrated with electronic circuitry. This sensor can be fabricated on alumina or silicon substrates. The electrode material can be made up of nickel, gold or aluminum and the thickness of the electrodes ranges typically between 0.2 and 0.3 μm. The sensor consists of an active sensing layer on top of a set of electrodes. The design of the electrodes can be configured for both resistive and capacitive sensing.

The polyimide material's ohmic resistance changes significantly with humidity variations. Changes in resistance as large as 4‐6 orders of magnitude are attainable over the entire operational humidity range.

As the sensitivity varies non‐linearly with the humidity, the measurement has to be carried out over a very wide range in order to calibrate the sensor. The sensitivity and output range of the sensor can be easily controlled by changing the electrode spacing or geometry.

The control of humidity is important in many applications ranging from bio‐medical to space exploration.

A simple, easy to fabricate and measure, and low cost resistive‐type humidity sensor was developed. The realized sensor is suitable for integrating with microfabrication. Hence, multiple sensors of varying sensitivities and output ranges could be integrated on the same chip. Over the last few years, newly emerging micro‐electro‐mechanical‐systems technology and micro‐fabrication techniques have gained popularity and importance in the miniaturization of a variety of sensors and actuators.

The aim of this review is to present together the studies on textile-based moisture sensors developed using innovative technologies in recent years.

The integration levels of the sensors studied with the textile materials are changing. Some research teams have used a combination of printing and textile technologies to produce sensors, while a group of researchers have used traditional technologies such as weaving and embroidery. Others have taken advantage of new technologies such as electro-spinning, polymerization and other techniques. In this way, they tried to combine the good working efficiency of the sensors and the flexibility of the textile. All these approaches are presented in this article.

The presentation of the latest technologies used to develop textile sensors together will give researchers an idea about new studies that can be done on highly sensitive and efficient textile-based moisture sensor systems.

In this paper humidity sensors have been explained in terms of measuring principle as capacitive and resistive. Then, studies conducted in the last 20 years on the textile-based humidity sensors have been presented in detail. This is a comprehensive review study that presents the latest developments together in this area for researchers.

The aim of this study is to investigate the humidity-sensing of polyaniline–zinc oxide (PANI–ZnO) nanocomposites. Humidity sensor has wide applications in drug industries, food industries and domestic purpose to regulate the humidity level.

PANI–ZnO composites were prepared by in situ polymerization method, and further humidity response was tested by using a two-probe sensor setup.

PANI-ZnO composites surface were modified by using camphor sulphonic acid. DC conductivity is due to the hopping of polorans. Thermal coefficient value varies from 1.7 to 2.3. The 30 weight per cent composite shows high sensitivity among other composites.

These composites can be used only at room temperature or moderate temperature, i.e. below 280°C.

The composites are prepared in tetrapod shape that has a large surface area and more stability. Therefore, these materials would be the replacement for conventional materials.

These sensors have many applications in food and drug preservation, domestic purposes, etc.

This work is original, and not being considered for publication elsewhere. In this work, the charge transport properties were evaluated based on the resistivity change when samples were exposed to humidity.

Explains the problems, often unrecognized by engineers, which can be caused by excessive humidity in manufacturing, and identifies the confusion surrounding the measurement of humidity, which may account for the low level of recognition. Reports on the measures being taken to eliminate that confusion and some of the instruments currently available to measure humidity. Outlines the main technologies available to correct excess humidity and their qualities.

This paper aims to encompass the technological advancements in the area of flexible sensing electronics fabrication particularly for wearable device development applications. In the recent past, it is evident that there is a tremendous growth in the field of flexible electronics and sensors fabrication technologies all around the world. Even though, there is a significant amount of research has been carried in the past decade, but still there is a huge need for exploring novel materials for low temperature processing, optimized printing methods and customized printing devices with accurate feature control.

The author has done an extensive literature survey in the proposed area and found that the researchers are showing significant interest in exploring novel materials, new conductive ink processing methods suitable for additive manufacturing, and fabrication technologies for developing the plastic substrate-based flexible electronics for the on growing demands of wearable devices in the market.

The author has consolidated some of the recent advancements in the area of flexible sensing electronics using the inkjet-printing platform carried out by the researchers. The novel customized inkjet-printing technology, materials selections for device development, compatibility of the materials for the inkjet-printing process and the interesting results of the devices fabricated are highlighted in this paper.

The author has reported the novel inkjet-printing platforms explored by researchers in the recent past for various applications which primarily includes gas sensing. The author has consolidated in a crisp manner about the technology, materials compatible for inkjet-printing, and the exciting results of the printed devices. The author has reported the advantages and challenges of the proposed methods by the researchers. This work will bridge the technical gap in the inkjet-printing technology and will be useful for the researchers to take forward the research work on this domain to the next level.

The purpose of this paper is to propose and optimize plastic optical fiber (POF) probe with macro-bending biconical tapered structure for the relative humidity (RH) sensing.

In this study, the principle is the evanescent wave power modulated by the ambient humidity. The probe is fabricated by using fused biconical taper and heat-setting method and then coated with a fluorescent moisture-sensitive film.

The probe’s sensing performance can be optimized by changing the probe’s curvature radius, biconical tapered transition length and taper waist diameter. The result shows that the sensitivity of the probe is up to 1.60 and 3.40 mV/ per cent, respectively, at low humidity (10-45 per cent) and high humidity (45-90 per cent). Also, this probe has good linearity, repeatability, photostability and long-term stability.

The proposed probe can improve the sensitivity and linearity of RH sensing without complex devices, which is necessary for mass production, remote measurement and convenient operation.

POF probe with macro-bending biconical tapered structure is investigated in this paper, which is proved to be effective in improving the sensitivity and linearity.

In this paper, we propose a new way for the determination of a_w in fresh and salt meat. The principle is founded on the analysis of a small air volume inside the product. First we describe the fundamental definition of water activity, the state‐of‐the‐art of commercial a_w meters, the effects of a_w on microbiology in food. In the second step, after a description of the sensor, the principle and the procedure of measurement are explained. The measurements of a_w are realized in meat at different stages of drying. Reproducibility and the temperature effect are particularly analyzed.

This paper aims to show that by using air source heat pump (ASHP) water heater in the residential sector, the energy consumption from sanitary hot water production can be reduced by more than 50 per cent. Hence, this study quantitatively and qualitatively confirms that domestic ASHP water heater is a renewable and energy efficient device for sanitary hot water production.

Design and building of a data acquisition system comprises a data logger, power meters, flow meters, temperature sensors, ambient and relative humidity sensor and an electronic input pulse adapter to monitor the ASHP water heater performance. All the sensors are accommodated by the U30-NRC data logger. The temperature sensors are installed on the inlet pipe containing a flow meter and the outlet pipe of the ASHP unit, the vicinity of both evaporator and expel cold air. An additional temperature sensor and a flow meter that cater for hot water drawn off measurements are incorporated into the data acquisition system (DAS).

The result from a specific monitoring split type ASHP water heater gives an average daily coefficient of performance (COP) of 2.36 and the total electrical energy of 4.15 kWh, and volume of hot water drawn off was 273 L. These results were influenced by ambient temperature and relative humidity.

The cost involved in purchasing the entire sensors and data logger limits the number and categories of ASHP water heaters whose performance were going to be monitored. Pressure sensors were excluded in the data acquisition system.

The data acquisition system can easily be designed and the logger can also be easily programed. Hence, no high technical or computer skills are needed to install the DAS and to be able to read out the results.

Hence, the data acquisition system can be installed on the entire domestic Eskom roll out air source heat pump water heaters to effectively determine the coefficient of performance and demand reductions.

This DAS is the first of its kind to be built in South Africa to be used to determine the performance of an ASHP water heater with high accuracy and precision. DAS is also robust.