Low Humidity Characteristics of Polymer-Based Capacitive Humidity Sensors

Majewski, Jacek

doi:10.1515/mms-2017-0048

Cited by 10 publications

(3 citation statements)

References 24 publications

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“…Some of the most recent relative humidity sensors have employed new materials as moisture-sensitive layers. These materials include porous ceramic oxides [9], [10], polymers [11], [12], and electrolytes [13], [14]. Ceramic oxides can be prepared by conventional or advanced processing, and their extensive use as humidity sensors is due to their hydrophilic nature, so water vapor can easily penetrate through the pore openings.…”

Section: Introductionmentioning

confidence: 99%

The Effect of SnO2 Mixture on a PVA-Based Thick Film Relative Humidity Sensor

Wiranto¹,

Martadi²,

Sulthoni³

et al. 2022

International Journal on Advanced Science, Engineering and Information Technology

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In this research, thick film technology has been used to design and fabricate relative humidity sensors with Polyvinyl Alcohol (PVA) as the sensing layer. The design was optimized to produce an ideal geometry according to the limitations of thick film technology. The sensor fabrication process used screen printing techniques on Alumina (Al2O3) substrate with Silver (Ag) as the electrode material. SnO2 was added to the PVA sensing layer with variations in the composition of 1:1 and 1:2. FTIR analysis showed that the addition of SnO2 did not affect the structure of the PVA, which indicated that there was no chemical reaction between PVA and SnO2. The deposition of the sensing layer was carried out using spin coating method, and the fabricated sensors were then tested by varying 5 humidity points inside a chamber with a hygrometer as a reference. Based on the test results, it was found that the sensors showed responses to humidity variation in the form of changes in resistance values. When the humidity in the chamber increased, the sensor resistance value decreased. The addition of SnO2 could reduce the relatively high resistance value of the PVA-based humidity sensor and also increase the sensor's time response to humidity variation. However, the humidity sensor's sensitivity decreased for the higher composition of SnO2. With this technique, a simple yet stable humidity sensor could be fabricated using thick-film technology with a wide range of potential applications.

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Section: Introductionmentioning

confidence: 99%

The Effect of SnO2 Mixture on a PVA-Based Thick Film Relative Humidity Sensor

Wiranto¹,

Martadi²,

Sulthoni³

et al. 2022

International Journal on Advanced Science, Engineering and Information Technology

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“…In the Kapton ® structure, the carboxyl groups –C=O are the primary bonding sites for the adsorption of water vapor molecules. Also, the ether groups C–O–C and N–C groups can constitute adsorption sites [ 20 ].…”

Section: Discussionmentioning

confidence: 99%

Humidity Measurement in Carbon Dioxide with Capacitive Humidity Sensors at Low Temperature and Pressure

Lorek

Majewski

2018

Sensors

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In experimental chambers for simulating the atmospheric near-surface conditions of Mars, or in situ measurements on Mars, the measurement of the humidity in carbon dioxide gas at low temperature and under low pressure is needed. For this purpose, polymer-based capacitive humidity sensors are used; however, these sensors are designed for measuring the humidity in the air on the Earth. The manufacturers provide only the generic calibration equation for standard environmental conditions in air, and temperature corrections of humidity signal. Because of the lack of freely available information regarding the behavior of the sensors in CO2, the range of reliable results is limited. For these reasons, capacitive humidity sensors (Sensirion SHT75) were tested at the German Aerospace Center (DLR) in its Martian Simulation Facility (MSF). The sensors were investigated in cells with a continuously humidified carbon dioxide flow, for temperatures between −70 °C and 10 °C, and pressures between 10 hPa and 1000 hPa. For 28 temperature–pressure combinations, the sensor calibration equations were calculated together with temperature–dependent formulas for the coefficients of the equations. The characteristic curves obtained from the tests in CO2 and in air were compared for selected temperature–pressure combinations. The results document a strong cross-sensitivity of the sensors to CO2 and, compared with air, a strong pressure sensitivity as well. The reason could be an interaction of the molecules of CO2 with the adsorption sites on the thin polymeric sensing layer. In these circumstances, an individual calibration for each pressure with respect to temperature is required. The performed experiments have shown that this kind of sensor can be a suitable, lightweight, and relatively inexpensive choice for applications in harsh environments such as on Mars.

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“…With the development of an intelligent modern society, humidity sensors are widely used in multifarious fields such as environmental monitoring, 1 automobile defogging, 2 production line, 3 respiratory monitoring, 4–6 medical care, 7 agriculture and forestry breeding, 8 meteorological detection, 9 food logistics and transportation, 10 and wearable flexible equipment. 11 As a precision instrument for humidity measurement, it is highly vital for a humidity sensor to satisfy higher requirements for its accuracy, sensitivity, excellent stability and compatibility.…”

Section: Introductionmentioning

confidence: 99%