Capacitance Humidity Sensor

1995 ◽  
Vol 382 ◽  
Author(s):  
Andrew R.K. Ralston ◽  
Paul E. Thoma ◽  
Carl F. Klein ◽  
Denice D. Denton
Keyword(s):  
Water Vapor ◽  
Chemical Composition ◽  
Relative Humidity ◽  
Humidity Sensor ◽  
Moisture Uptake ◽  
Free Standing ◽  
Sorption Model ◽  
Volume Calculations ◽  
Water Vapor Transmission ◽  
Design Construction

ABSTRACTA capacitance relative humidity (RH) sensor is described that has a design, construction, and material composition that result in an inexpensive and robust sensor. This sensor has a multilayer, free-standing film construction. It consists of a humidity sensitive polyimide (PI) dielectric core and conductive layers consisting of carbon filled polysulfone on each side of the polyirnide film to form a capacitor. The polyimide used is a BPDA-ODA type, and replaces a PMDA-ODA type polyimide used in a previous version of this sensor. The BPDA-ODA sensor has a nominal capacitance of 200 pF and a nominal sensitivity of 13% at 100% RH. The characteristics of this humidity sensor are discussed and compared to the characteristics of the PMDA-ODA type sensor. Characteristics considered include the PI film moisture uptake and water vapor transmission, and the sensors' sensitivity to relative humidity, frequency response, and aging at 85°C/85% RH. The dual-state sorption model and free volume calculations are used to demonstrate that observed differences in the film are due to differences in chemical composition between the films.

Effect of Anthocyanin Preparations as Colorants on Hygroscopicity of Dry-Pack Foods

1979 ◽  
Vol 42 (3) ◽  
pp. 225-227 ◽  
Author(s):  
F. M. CLYDESDALE ◽  
J. H. MAIN ◽  
F. J. FRANCIS ◽  
K. M. HAYES
Keyword(s):  
Water Vapor ◽  
Relative Humidity ◽  
Transmission Rate ◽  
Packaging Material ◽  
Physical Parameters ◽  
Water Vapor Transmission Rate ◽  
Natural Colorants ◽  
Water Vapor Transmission ◽  
Grape Skins ◽  
Equilibrium Relative Humidity

The equilibrium relative humidity isotherm of a cherry beverage base and a strawberry gelatin dessert mix colored with anthocyanins from grape skins, cranberries and roselle was evaluated versus a Red No. 2 control. As well, the water vapor transmission rate of the packaging material was evaluated to evaluate probable shelf-life. Results indicated that physical parameters, such as hygroscopicity, must be considered in estimating effects of the use of natural colorants in foods as well as the color and chemical stability normally investigated.

scholarly journals Characterization and Corrections of Relative Humidity Measurement from Meteomodem M10 Radiosondes at Midlatitude Stations

2020 ◽  
Vol 37 (5) ◽  
pp. 857-871
Author(s):  
Jean-Charles Dupont ◽  
Martial Haeffelin ◽  
Jordi Badosa ◽  
Gaelle Clain ◽  
Christophe Raux ◽  
...  
Keyword(s):  
Water Vapor ◽  
Relative Humidity ◽  
Humidity Sensor ◽  
Global Climate ◽  
Time Lag ◽  
Capacitive Sensor ◽  
Cold Temperatures ◽  
Humidity Measurements ◽  
Main Effects ◽  
Very High

AbstractMeasurement of water vapor or humidity in the atmosphere is fundamental for many applications. Relative humidity measurements with a capacitive sensor in radiosondes are affected by several factors that need to be assessed and corrected. This work aims to address corrections for the main effects for the Meteomodem M10 radiosonde as a step to meet the Global Climate Observing System (GCOS) Reference Upper-Air Network (GRUAN) requirements. The considered corrections are 1) the calibration correction; 2) a slow regime due to the slow diffusion of molecules through the sensor, especially at very high and very low relative humidity conditions; 3) the relative humidity sensor dependence on the gradient of temperature; and 4) the time lag at cold temperatures, which affects measurements in regions of strong relative humidity gradients. These corrections were tested for 26 nighttime and 25 daytime radiosondes in two midlatitude locations for which both Meteomodem M10 and Vaisala RS92 measurements were available. The results show that, after correcting for the four effects, M10 relative humidity measurements are, on average, consistent with the Vaisala RS92 relative humidity values within 2% RH at all altitudes for the nighttime launches (against 6% RH before the correction) and within 5% RH at all altitudes for the daytime launches (against 9% RH before the correction).

Multilayer test method for water vapor transmission testing of construction materials

2012 ◽  
Vol 35 (3) ◽  
pp. 224-237 ◽  
Author(s):  
Marcin Pazera ◽  
Mikael Salonvaara
Keyword(s):  
Water Vapor ◽  
Relative Humidity ◽  
Strong Dependence ◽  
Construction Materials ◽  
Test Method ◽  
Water Vapor Transport ◽  
Novel Approach ◽  
Water Vapor Transmission ◽  
Using Data ◽  
Stacked Material

Water vapor transmission (WVT) measurements conducted with highly permeable materials are complicated by the instability of boundary conditions, more specifically by changes in vapor pressure and air velocity on either or both sides of the specimen. Such effects pose a greater challenge in determining the water vapor transport characteristics of thin, flexible, and highly permeable construction materials. This article presents a novel approach to WVT testing that improves some of these issues. The approach denoted as ‘multilayer test’ involves testing simultaneously several vertically stacked material layers each separated by air gap with equal thickness. Wireless relative humidity and temperature sensors mounted on the opposing surfaces of each layer provide continuous temperatures and relative humidity monitoring near the specimen surfaces. The test is conducted in a controlled environment with the set-up kept on an analytical balance. Change in the weight of the system is determined automatically at predetermined time intervals, and fluxes are calculated. Two approaches are used in determining the permeance of each material layer. The results of both approaches are compared. The multilayer WVT tests provide several benefits over traditional ‘Dry’ or ‘Wet’ cup WVT test method in that; the boundary layer effects due to moving air above the specimen surface can be accounted for, and simultaneous testing of multiple specimens provides greater statistical confidence. The method is particularly advantageous in cases when the transport coefficient has a strong dependence on moisture content. Using data from a single multilayer test, a continuous transport function can be derived. This article highlights that the multilayer test approach leads to significant reduction in experimental effort, resources required for testing, and test durations, and improves the precision of the material property data.

MATHEMATICAL CORRELATION OF TEST METHODS FOR MEASURING WATER-VAPOR TRANSMISSION THROUGH FABRICS

2015 ◽  
Vol 18 (3) ◽  
pp. 245-255
Author(s):  
Teodor-Cezar Codau ◽  
Elena Onofrei ◽  
Stojanka Petrusic ◽  
Gauthier Bedek ◽  
Daniel Dupont ◽  
...  
Keyword(s):  
Water Vapor ◽  
Test Methods ◽  
Mathematical Correlation ◽  
Water Vapor Transmission
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