• Journal of Sensor Science and Technology
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• v.21 no.6
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• pp.420-424
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• 2012

We have investigated temperature dependence and long-term change of humidity measurement from 32 relative humidity sensors. The readings of the humidity sensors depended not only the reference humidity, but also temperature of the chamber. Approximately, the temperature dependence of the humidity sensor in average was 0.05 %R.H./$^{\circ}C$ in the temperature range from $5^{\circ}C$ to $55^{\circ}C$. For humidity sensors that have an internal temperature compensation circuit, the resulting temperature dependence was weaker by 20%. It should be also noted that for the humidity sensors used in this work underwent ${\pm}3$ %R.H. change per year for level of confidence of 95%. The users of relative humidity sensors may refer this value as a minimum change when they set the calibration interval of the humidity sensors.

• Proceedings of the KIEE Conference
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• 1997.07d
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• pp.1311-1313
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• 1997

We describe the working principle, the design, and the characteristics of two-chip integrated humidity sensor. The sensing element was manufactured using polyimide. The interface circuits were developed based on a charge redistribution between capacitors. The sensor and signal conditioning chips were packaged together in the same package. The sensor showed excellent linearity over a wide range of relative humidity.

• Transactions on Electrical and Electronic Materials
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• v.14 no.4
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• pp.182-186
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• 2013

We studied the possibility that an air capacitor can be used as a humidity sensor by measuring capacitance change. In order to investigate the possibility, the change of capacitance of an air capacitor due to moisture in air was first considered theoretically, and was then experimentally verified. The capacitance was measured by an LCR impedance meter with a 100-kHz and 1-V ac. The results revealed that the changes in the experimentally measured capacitances were greater than those in the theoretically calculated values. Based on this fact, we knew that an air capacitor could be used as part of a humidity sensing device. We expect the humidity sensor with an air capacitor has characteristics of fast response time, high reliability, and high durability compared with other conventional methods.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.27 no.9
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• pp.566-570
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• 2014

Electrode pattern effects on the capacitive humidity sensor were investigated. The fabrication of the capacitive humidity sensor was formed with three steps. The bottom electrode was formed on the silicon substrate with Pt/Ti thin layer by using shadow mask and e-beam evaporator. The photo sensitive polyimide was formed on the bottom electrode by using photolithography process as a humidity sensitive thin film. The upper electrode was formed on the polyimide thin film with Pt/Ti thin layer by using e-beam evaporator and lift-off method. Three electrode patterns, such as circle, square, and triangle pattern, were used and changed the sizes to investigate the effects. The capacitances of the sensors were decreased 622 to 584 pF with the area decreament of patterns 250,000 to $196,250{\mu}m^2$. From these results, a capacitive humidity sensor with photo sensitive polyimide is expected to be applied to a high sensitive humidity sensor.

• Journal of Sensor Science and Technology
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• v.13 no.4
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• pp.287-291
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• 2004

A capacitive type humidity sensor has been fabricated using a polyimide film without hydrophobic elements and its characteristics has been evaluated for hermeticity measurement of micro packages. For a highly sensitive humidity sensor, a polyimide film without hydrophobic elements has been synthesized and used instead of using a commercial one in which 7 group elements such as fluorine or chlorine are included. Sensitivity, stability and hysteresis has been performed to characterize the fabricated sensors. The sensitivity defined as normalized percent capacitance change was 0.3751%RH and hysteresis was 0.77% in the range of 10%RH to 90%RH. Maximum deviation from the average capacitance measured for 120 minutes at 50%RH was 0.25%. The proposed humidity sensor can be used for hermeticity measurement of micro packages.

• Journal of the Korean Society of Safety
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• v.19 no.3 s.67
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• pp.51-56
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• 2004

Conductive polymer blends and composites are widely used for different safety application such as electrostatic charge dissipation(ESD), electromagnetic interference(EMI) shielding, electrostatic prevention and safety chemical sensor. In order to prepare a impedance-type humidity sensor that is durable at high humidities and high temperature, electically conductive polymer blends based on diallyldimethylammonium chloride(DADMAC) and epoxy were prepared in this study. The polymer blends type conductive ionomer exhibits reaction each other DADMAC and epoxy in FT-IR and DSC analysis. The blends material was traced by new peak at 1600cm-1 and appeard improvement of thermal resistance by melting point shift. Alumina substrate was deposited a pair of gold electrodes by screen printing. The blend material were spin-coated with a thin film type on the surface of alumina substrate. The polymer bleld type sensor exhibits a linear impedance increasing better than DADMAC coated humidity sensor. Also it shows good sensitivity, low hysteresis and durability against high humidity.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.1515_1516
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• 2009

A 440MHz wireless and passive surface acoustic wave (SAW) based micro-sensor was developed for simultaneous measurement of temperature and humidity. The developed sensor is composed of a SAW reflective delay lines structured by an IDT (Inter-Digital Transducer), four reflectors and humidity sensitive film (polyimide). Polyimide was dry-ecthed by RIE (Reactive Ion Etching) to obtain high roughness, which gives the large reaction area resulting in high sensitivity. In wireless testing using a network analyzer, sharp reflection peaks with high S/N ratio, small signal attenuation, and few spurious peaks were observed in the time domain. High sensitivity towards the temperature and humidiy were also observed in the large concentration range. The obtained sensitivity was $16.8^{\circ}/^{\circ}C$ for temperature sensor and $15.8^{\circ}$/%RH for humidity sensor.

• Journal of Korea Society of Industrial Information Systems
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• v.19 no.2
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• pp.31-36
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• 2014

In this paper, we developed an intergrated piezoresistive temperature and humidity sensor using nano-technology, and evaluated the properties. In the measuring range from $20^{\circ}C$ to $80^{\circ}C$, output sensitivity of temperature was about 0.75mV/$1^{\circ}C$. Output sensitivity of humidity was about 1.35mV/10%(RH). Therefore, developed sensor suggests that it is possible applicable to the general residential environment.

• Journal of Sensor Science and Technology
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• v.12 no.6
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• pp.241-248
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• 2003

An electrochemical humidity sensor was fabricated with poly(1,5-diaminonaphthalene) film coated on a gap of two splitted gold electrodes, which were made by vacuum deposition. Response currents according to humidity were measured by the potential sweep method and chronoamperometry. The stability of the polymer film was improved by double step chronoamperometry using the applied voltage of ${\pm}0.5$ Vdc. The response time determined by the pulse technique was about ${\sim}50$ msec and the relative standard deviation of current response was within ${\pm}5.0%$. The response current of the film was intrinsically humidity dependent. The film exhibited a non-linear but reproducible response in ordinary range of relative humidity. The linear equations were $I(nA)=0.28{\times}%RH-1.01$ between 10 to 70 %RH and $I(nA)=6.05{\times}%RH-403.21$ between 70 to 90 %RH.

• Macromolecular Research
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• v.13 no.3
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• pp.265-272
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• 2005

Polyelectrolyte membranes for humidity-sensing were fabricated using a layer-by-layer adsorption process based on the spontaneous self-assembly of alternating layers of cationic and anionic polymers on a silanized ITO patterned glass substrate. The substrate is dipped successively into dilute solutions of a polyanion and a polycation. The homopolymers and copoymers of diallyldimethylammonium chloride (DDA), allylamine hydrochloride (AA), 2-[(methacryloyloxy)ethyl]trimethyl ammonium chloride (METAC) and vinylbenzyl tributyl phosphonium chloride(VTBPC) were used as the polycations. In this experiment, it was found that the resistance varied according to the chemical structure of the polycation. The resistance varied from $10^7$ to $10^5$ $\Omega$, as the humidity was increased from 60 (relative humidity) to $95\%$RH, which is the range of RH values required for a dew sensor operating at high humidity.