WO2020183068A1 - A humidity and temperature measuring device and method of measuring - Google Patents

A humidity and temperature measuring device and method of measuring Download PDF

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Publication number
WO2020183068A1
WO2020183068A1 PCT/FI2020/050159 FI2020050159W WO2020183068A1 WO 2020183068 A1 WO2020183068 A1 WO 2020183068A1 FI 2020050159 W FI2020050159 W FI 2020050159W WO 2020183068 A1 WO2020183068 A1 WO 2020183068A1
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WO
WIPO (PCT)
Prior art keywords
air
measuring device
humidity
calcium sulfate
sulfate dihydrate
Prior art date
Application number
PCT/FI2020/050159
Other languages
French (fr)
Inventor
Jaakko ALA-PAAVOLA
Marko Oikarinen
Original Assignee
Mato Engineering Oy
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Mato Engineering Oy filed Critical Mato Engineering Oy
Publication of WO2020183068A1 publication Critical patent/WO2020183068A1/en

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
    • G01D11/00—Component parts of measuring arrangements not specially adapted for a specific variable
    • G01D11/24—Housings ; Casings for instruments
    • G01D11/245—Housings for sensors
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N1/00—Sampling; Preparing specimens for investigation
    • G01N1/02—Devices for withdrawing samples
    • G01N1/22—Devices for withdrawing samples in the gaseous state
    • G01N1/2202—Devices for withdrawing samples in the gaseous state involving separation of sample components during sampling
    • G01N1/2205—Devices for withdrawing samples in the gaseous state involving separation of sample components during sampling with filters
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
    • G01K1/00—Details of thermometers not specially adapted for particular types of thermometer
    • G01K1/14—Supports; Fastening devices; Arrangements for mounting thermometers in particular locations
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N19/00—Investigating materials by mechanical methods
    • G01N19/10—Measuring moisture content, e.g. by measuring change in length of hygroscopic filament; Hygrometers
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
    • G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
    • G01N21/35—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light
    • G01N21/3554—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light for determining moisture content
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N22/00—Investigating or analysing materials by the use of microwaves or radio waves, i.e. electromagnetic waves with a wavelength of one millimetre or more
    • G01N22/04—Investigating moisture content
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N25/00—Investigating or analyzing materials by the use of thermal means
    • G01N25/56—Investigating or analyzing materials by the use of thermal means by investigating moisture content
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance
    • G01N27/04—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance
    • G01N27/048—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance for determining moisture content of the material
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance
    • G01N27/04—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance
    • G01N27/12—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance of a solid body in dependence upon absorption of a fluid; of a solid body in dependence upon reaction with a fluid, for detecting components in the fluid
    • G01N27/121—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance of a solid body in dependence upon absorption of a fluid; of a solid body in dependence upon reaction with a fluid, for detecting components in the fluid for determining moisture content, e.g. humidity, of the fluid
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance
    • G01N27/22—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating capacitance
    • G01N27/223—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating capacitance for determining moisture content, e.g. humidity
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/60—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrostatic variables, e.g. electrographic flaw testing
    • G01N27/605—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrostatic variables, e.g. electrographic flaw testing for determining moisture content, e.g. humidity
    • G—PHYSICS
    • G12—INSTRUMENT DETAILS
    • G12B—CONSTRUCTIONAL DETAILS OF INSTRUMENTS, OR COMPARABLE DETAILS OF OTHER APPARATUS, NOT OTHERWISE PROVIDED FOR
    • G12B9/00—Housing or supporting of instruments or other apparatus
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance
    • G01N27/22—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating capacitance
    • G01N27/223—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating capacitance for determining moisture content, e.g. humidity
    • G01N27/225—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating capacitance for determining moisture content, e.g. humidity by using hygroscopic materials

Definitions

  • the invention relates to a humidity and temperature measuring device, and particularly a humidity and temperature measuring device for measuring air humidity and temperature, and method of measuring with the humidity and temperature measuring device.
  • humidity content of gases is measured capacitively such that a sensing element is in direct contact with the free-flowing gas.
  • the measurement is based on a change caused by humidity in the measured capacitance.
  • the sensing elements are protected for example from solid particles such as dust by filter structures made of sintered metal or porous polymer.
  • filter structures made of sintered metal or porous polymer.
  • impurities of the measured air such as acidity and alkalinity and corrosion, which cause reliability problems of the measuring device.
  • An object of the invention is to solve the above described problem relating to a humidity and temperature measuring device.
  • the object is achieved by a solution according to the invention, which is characterized in that the measuring device comprises a closed casing part, an air-filled cavity inside the casing part, and a humidity sensor and a temperature sensor provided in the cavity, and the casing part comprises a part made of calcium sulfate dihydrate, and the air to be measured passes to the cavity through the part made of calcium sulfate dihydrate.
  • the casing part of the measuring device protects the sensing elements, the humidity sensor and the temperature sensor from impurities. By this a good measurement accuracy of the measuring device in different conditions is achieved and the measurement accuracy will not diminish over time.
  • the measuring device is placed in contact with the air to be measured, for example in an open air space, such that the air to be measured surrounds the measuring device, or such that the casing part made of calcium sulfate dihydrate is in contact with the air to be measured.
  • the air to be measured and in particularly humidity in the air, i.e. the water vapor passes through the casing part made of calcium sulfate dihydrate to the cavity comprising the sensors.
  • the casing part made of calcium sulfate dihydrate forms a filter to the air to be measured and filters impurities from the air to be measured before the air to be measured flows to the air-filled cavity.
  • the casing part made of calcium sulfate dihydrate has a neutralizing property, thereby reducing the effect of acidic or alkaline vapors, and additionally binds any salts present in the water vapor. Both properties improve the accuracy of the measurement and reduce the corrosion inside the instrument, thus extending its operating time.
  • Humidity transfers hygroscopic and/or capillary through the casing part made of calcium sulfate dihydrate.
  • the casing part made of calcium sulfate dihydrate is moisture resistant. Temperature transfers through the casing part to the air-filled cavity.
  • Humidity and temperature measuring device and method comprises a casing part made of calcium sulfate dihydrate which makes the measuring device hydroscopic and the method hydroscopic.
  • the casing part made of calcium sulfate dihydrate binds water vapor and releases water vapor whenever there is a partial pressure difference in water vapor between the pores of the casing and the surrounding air. So, the humidity and temperature of the air-filled cavity within the measuring device seeks equilibrium with the outside air. Hereby measuring the relative humidity and temperature of the air-filled cavity, the humidity and temperature of the air to be measured are determined.
  • the measuring device is particularly suitable for measuring humidity in conditions of particulate contamination such as dust, condensing moisture, freezing, corrosive or oxidizing conditions.
  • the casing part protects the humidity sensor and the temperature sensor located in the cavity from dust, mechanical stress and corrosion caused by acid.
  • Calcium sulfate dihydrate is inexpensive as a material and very easy to produce as mold casting various casing structures. Calcium sulfate dihydrate is also stable enough as a material to be used as a casing part and withstands long-term exposure to outdoor air. A casing part made of calcium sulfate dihydrate withstands well changes in temperature and humidity. A casing part made of calcium sulfate dihydrate does not either rust or rot or, to a lesser extent, deteriorate during use.
  • the entire casing part surrounding the air-filled cavity is made of calcium sulfate dihydrate.
  • the casing part comprises a part made of calcium sulfate dihydrate, and another part, which is substantially watertight. Water tightness is achieved, for example, by polymer- based material casting.
  • the measuring device comprises a radio transmitter, an antenna and a power source, provided in the cavity.
  • the measuring device can then be connected to the radio network to transfer the measurement data stored in the memory in the cavity to the receiving device.
  • the measuring device can be connected to the Internet of Things (IoT) data network with low power consumption wireless wide area network (Low Power Wide Area Network, LPWAN).
  • IoT Internet of Things
  • LPWAN Low Power Wide Area Network
  • Low power consumption wireless wide area networks technologies and standards are SigFox, LoRa and Weightles.
  • the measurement data can be transferred for example to a cloud service.
  • Communication technologies based on cellular technologies and networks, such as NB-IOT and Cat-M, may also be used for the transmission of the measurement data.
  • the measurement device may also be connected, for example, by means of wires or cables, to a measuring data receiver device.
  • the measurement device comprises a cover case, where the casing part is placed, and the cover case comprises one or more air flow openings.
  • An advantage of the cover case is the protection against breakage of the measurement device.
  • the air flow openings in the cover case allow airflow into and out of the measurement device.
  • the cover case may be made of, for example, plastic, metal or wood.
  • the method comprises a humidity and temperature measuring device.
  • the part of the humidity and temperature measurement device made of calcium sulfate dihydrate is placed in contact with the air to be measured.
  • the air to be measured flows through the part made of calcium sulfate dihydrate to the cavity to the humidity sensor and to the temperature sensor placed in the cavity.
  • the humidity sensor measures the relative humidity of air and the temperature sensor measures the air temperature.
  • Figure 1 shows a cross-section of the temperature and humidity measuring device
  • Figure 2 shows a cross-section of the temperature and humidity measuring device
  • Figure 3 shows a cross-section of the temperature and humidity measuring device
  • FIGS 4, 5 and 6 show further alternative embodiments of the measuring device.
  • Figure 1 shows a cross-section of a temperature and humidity measuring device.
  • the humidity and temperature measuring device comprises a closed casing part 1.
  • An air-filled cavity 2 is provided inside the casing part 1.
  • a humidity sensor 3a and a temperature sensor 3b are provided in the cavity 2.
  • the casing part 1 is made of calcium sulfate dihydrate. Air 4 to be measured and in particularly its water vapor is transferred to the cavity 2 through the part 1 made of calcium sulfate dihydrate.
  • the humidity and temperature inside the cavity provided inside the measuring device seeks equilibrium with outside air 4.
  • the relative humidity and temperature values measured by the humidity sensor 3a and the temperature sensor 3b located in the cavity 2 correspond to the relative humidity and temperature values of the measured air 4.
  • Figure 2 shows a cross-section of the temperature and humidity measuring device, in which the casing part 1, lb is different than in the figure 1.
  • the casing part 1, lb comprises a part 1 made of calcium sulfate dihydrate and an other casing part lb.
  • the other casing part lb is of different material than the part 1 made of calcium sulfate dihydrate.
  • the other casing part lb may be for example substantially watertight, whereby the water vapor of the air 4 to be measured has to pass through the casing part 1 made of calcium sulfate dihydrate to enter the cavity 2.
  • Figure 3 shows a measuring device, which comprises a cover case 6.
  • the measuring device is placed in an open-air space 4, which is the air to be measured.
  • the casing part 1, lb is placed within the cover case.
  • the cover case 6 comprises multiple air flow openings 7, through which the air to be measured can flow into the casing part 1, lb.
  • the cover case 6 protects the casing part 1, lb from mechanical breakage.
  • the casing part 1, lb comprises a part 1 made of calcium sulfate dihydrate and a casing part lb made of other material. Air flow openings 7 are provided towards the part 1 made of calcium sulfate dihydrate. If the casing part 1, lb is made largely of the part 1 made of calcium sulfate dihydrate it is preferable to provide air flow openings 7 over the entire area of the cover case 6.
  • the measuring device further comprises a radio transmitter, an antenna and a power source 5 placed in the air-filled cavity 2.
  • the casing part 1, lb and the cover case 6 shown in figures 1-3 are not thermally insulated, wherein the temperature of the cavity 2 settles to the ambient temperature.
  • the humidity sensor 3a and the temperature sensor 3b are preferably electrical sensors. Thereby the humidity sensor 3a and the temperature sensor 3b have a power supply in the cavity, for example a battery, or they are connected to a power supply outside the cavity 2.
  • the humidity sensor 3a may be for example a capacitive humidity sensor comprising a capacitive sensing element such as for example two electrodes and a water sensitive material placed between. A sensitive material absorbs moisture from the surrounding air, which causes a change in capacitance. Capacitive humidity sensors have the advantage of their sensitivity, wide measuring range and stability.
  • the temperature sensor 3b may be, for example, a resistance thermometer or a thermocouple.
  • FIG. 4 shows one embodiment of the measurement device according to the present invention.
  • the measurement device comprises a closed air-filled chamber 200.
  • the measurement device comprises chamber walls lb defining a closed air-filled chamber space 2 inside the closed air-filled chamber 200.
  • the chamber walls lb are provided air and water vapour impermeable such that air and water vapour may not flow through the chamber walls lb.
  • the chamber walls lb have an outer chamber wall surface 14 and an inner chamber wall surface 12.
  • the inner surface defines the closed air-filled chamber space 2.
  • the chamber walls lb comprise a flow channel 18 between the closed the closed air-filled chamber space 2 inside the closed air-filled chamber 200 and the outside of the closed air filled chamber 200, as shown in figure 4.
  • the flow channel 18 is provided with a first barrier element 1 arranged to the flow channel 18.
  • the first barrier element 1 blocks or closes the flow channel 18.
  • the first barrier element 1 is arranged to define the closed air-filled chamber space 2 together with the chamber walls lb.
  • the first barrier element 20 comprises a first barrier inner surface 22 defining the closed air-filled chamber space 2 together with inner chamber wall surface 12 of the chamber walls lb.
  • the first barrier element 20 comprises a first barrier outer surface 24 defining outer surface of the closed air-filled chamber 200 together with outer chamber wall surface 14 of the chamber walls 10.
  • the first barrier element 1 is air and water vapour permeable enabling air and water vapour flow into and out of the closed air-filled chamber space 2 through the flow channel 18.
  • the measurement device further comprises a temperature sensor and humidity sensor 3a, b provided inside the air-filed chamber space 2 of the closed air-filled chamber 200.
  • the temperature sensor and humidity sensor 3a, b may be any know sensors.
  • Figure 5 shows one embodiment, comprising the closed air-filled chamber 200 of figure 4.
  • the measurement device comprises a cover case 6 surrounding the closed air-filled chamber 200.
  • the cover case 6 encloses the closed air-filled chamber 200.
  • the cover cas4 6 comprises an outer casing surface 44 forming the outer surface of the measurement device.
  • the cover casing 6 also comprises inner casing surface 42 towards the closed air-filled chamber 200.
  • the cover casing 6 is made of air and water vapour permeable material such that air and water vapour may pass through the cover casing to the flow channel 18 and further into and from the closed air-filled chamber space 2 through the first barrier element 1.
  • Figure 6 shows an embodiment, in which the measurement device comprises the first barrier elements 1 in the flow channel 18.
  • the measurement device further comprises the cover casing 6 surrounding and enclosing the closed air-filled chamber 200.
  • the cover casing 1 is made of air and water vapour impermeable material.
  • the housing is further provided with a housing barrier element 41.
  • the housing barrier element 41 is air and water vapour permeable and arranged to provide flow path for air and water vapour between the closed air- filled chamber 200 and outside of the cover casing 6.
  • the housing barrier element 41 is arranged in fluid communication with the flow channel 18 and the first barrier element 1 such that air and water vapour may flow between the outside of the cover casing 6 and the closed air-filled chamber space 2.
  • This first barrier element of figures 4, 5 and 6 is made of calcium sulfate dihydrate.
  • the watertight or air and water vapour impermeable of the chamber walls lb, or casing part lb may be polymer material, metal or the like preventing air and water vapour flow through the chamber walls lb.
  • the cover casing 6 is made of watertight or air and water vapour impermeable material.
  • the watertight or air and water vapour impermeable of the cover casing 6 may be polymer material, metal or the like preventing air and water vapour flow through the chamber walls lb.
  • the cover casing 6 is made of air and water vapour permeable material.
  • the air and water vapour permeable material of the cover casing 6 is porous material for providing air and water vapour permeability.
  • the air and water vapour permeable porous material may comprise mineral-based material, concrete, cement-based material or calcium sulfate dihydrate -based material or mixture thereof.
  • the housing barrier element 41 is made of air and water permeable material, preferably porous material.
  • the air and water vapour permeable porous material may comprise mineral-based material, concrete, cement-based material or calcium sulfate dihydrate -based material or mixture thereof.

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Abstract

The invention relates to humidity and temperature measuring device, which comprises a closed casign part (1, 1b), an air-filled cavity (2) inside the casing part (1, 1b) and a humidity sensor (3a) and a temperature sensor (3b) provided in the cavity (2), and the casing part (1, 1b) comprises a part (1) made of calcium sulfate dihydrate, and air (4) to be measured passes to the cavity (2) through the part (1) made of calcium sulfate dihydrate. The invention also relates to a method of measuring with the humidity and temperature measuring device.

Description

A HUMIDITY AND TEMPERATURE MEASURING DEVICE AND METHOD OF MEASURING
FIELD OF THE INVENTION
The invention relates to a humidity and temperature measuring device, and particularly a humidity and temperature measuring device for measuring air humidity and temperature, and method of measuring with the humidity and temperature measuring device.
BACKGROUND OF INVENTION
According to the prior art, humidity content of gases is measured capacitively such that a sensing element is in direct contact with the free-flowing gas. The measurement is based on a change caused by humidity in the measured capacitance.
Problem of the prior art is impurities that are brought into the sensing elements by the air that is measured by a measuring device, and inaccuracy in measurement caused by them over time.
The sensing elements are protected for example from solid particles such as dust by filter structures made of sintered metal or porous polymer. However, such structures have problems that are caused by impurities of the measured air such as acidity and alkalinity and corrosion, which cause reliability problems of the measuring device.
BRIEF DESCRIPTION OF THE INVENTION
An object of the invention is to solve the above described problem relating to a humidity and temperature measuring device. The object is achieved by a solution according to the invention, which is characterized in that the measuring device comprises a closed casing part, an air-filled cavity inside the casing part, and a humidity sensor and a temperature sensor provided in the cavity, and the casing part comprises a part made of calcium sulfate dihydrate, and the air to be measured passes to the cavity through the part made of calcium sulfate dihydrate.
The preferred embodiments of the invention are disclosed in the dependent claims.
The casing part of the measuring device protects the sensing elements, the humidity sensor and the temperature sensor from impurities. By this a good measurement accuracy of the measuring device in different conditions is achieved and the measurement accuracy will not diminish over time.
The measuring device is placed in contact with the air to be measured, for example in an open air space, such that the air to be measured surrounds the measuring device, or such that the casing part made of calcium sulfate dihydrate is in contact with the air to be measured. The air to be measured and in particularly humidity in the air, i.e. the water vapor passes through the casing part made of calcium sulfate dihydrate to the cavity comprising the sensors. The casing part made of calcium sulfate dihydrate forms a filter to the air to be measured and filters impurities from the air to be measured before the air to be measured flows to the air-filled cavity. The casing part made of calcium sulfate dihydrate has a neutralizing property, thereby reducing the effect of acidic or alkaline vapors, and additionally binds any salts present in the water vapor. Both properties improve the accuracy of the measurement and reduce the corrosion inside the instrument, thus extending its operating time.
The resistance of water vapor of calcium sulfate dihydrate, in general language gypsum, is low, whereby it does not form a remarkable flow resistance to the water vapor of the air to be measured. Instead air permeability coefficient of the calcium sulfate dihydrate is small. Humidity transfers hygroscopic and/or capillary through the casing part made of calcium sulfate dihydrate. The casing part made of calcium sulfate dihydrate is moisture resistant. Temperature transfers through the casing part to the air-filled cavity.
Humidity and temperature measuring device and method comprises a casing part made of calcium sulfate dihydrate which makes the measuring device hydroscopic and the method hydroscopic. The casing part made of calcium sulfate dihydrate binds water vapor and releases water vapor whenever there is a partial pressure difference in water vapor between the pores of the casing and the surrounding air. So, the humidity and temperature of the air-filled cavity within the measuring device seeks equilibrium with the outside air. Hereby measuring the relative humidity and temperature of the air-filled cavity, the humidity and temperature of the air to be measured are determined.
The measuring device is particularly suitable for measuring humidity in conditions of particulate contamination such as dust, condensing moisture, freezing, corrosive or oxidizing conditions. The casing part protects the humidity sensor and the temperature sensor located in the cavity from dust, mechanical stress and corrosion caused by acid.
Calcium sulfate dihydrate is inexpensive as a material and very easy to produce as mold casting various casing structures. Calcium sulfate dihydrate is also stable enough as a material to be used as a casing part and withstands long-term exposure to outdoor air. A casing part made of calcium sulfate dihydrate withstands well changes in temperature and humidity. A casing part made of calcium sulfate dihydrate does not either rust or rot or, to a lesser extent, deteriorate during use.
In one embodiment of the invention the entire casing part surrounding the air-filled cavity is made of calcium sulfate dihydrate.
According to one embodiment of the invention the casing part comprises a part made of calcium sulfate dihydrate, and another part, which is substantially watertight. Water tightness is achieved, for example, by polymer- based material casting.
According to one embodiment of the invention the measuring device comprises a radio transmitter, an antenna and a power source, provided in the cavity. The measuring device can then be connected to the radio network to transfer the measurement data stored in the memory in the cavity to the receiving device. For example, to transfer measurement data, can be connected to the Internet of Things (IoT) data network with low power consumption wireless wide area network (Low Power Wide Area Network, LPWAN). Examples of low power consumption wireless wide area networks technologies and standards are SigFox, LoRa and Weightles. Through the Internet of Things, the measurement data can be transferred for example to a cloud service. Communication technologies based on cellular technologies and networks, such as NB-IOT and Cat-M, may also be used for the transmission of the measurement data.
The measurement device may also be connected, for example, by means of wires or cables, to a measuring data receiver device.
According to one embodiment of the invention the measurement device comprises a cover case, where the casing part is placed, and the cover case comprises one or more air flow openings. An advantage of the cover case is the protection against breakage of the measurement device. The air flow openings in the cover case allow airflow into and out of the measurement device. The cover case may be made of, for example, plastic, metal or wood.
In the method of measuring humidity and temperature according to the invention, the method comprises a humidity and temperature measuring device. In the method the part of the humidity and temperature measurement device made of calcium sulfate dihydrate is placed in contact with the air to be measured. The air to be measured flows through the part made of calcium sulfate dihydrate to the cavity to the humidity sensor and to the temperature sensor placed in the cavity. The humidity sensor measures the relative humidity of air and the temperature sensor measures the air temperature.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention is described in detail by means of specific embodiments with reference to the enclosed drawings, in which
Figure 1 shows a cross-section of the temperature and humidity measuring device;
Figure 2 shows a cross-section of the temperature and humidity measuring device;
Figure 3 shows a cross-section of the temperature and humidity measuring device; and
Figures 4, 5 and 6 show further alternative embodiments of the measuring device.
DETAILED DESCRIPTION OF THE INVENTION
Figure 1 shows a cross-section of a temperature and humidity measuring device. The humidity and temperature measuring device comprises a closed casing part 1. An air-filled cavity 2 is provided inside the casing part 1. A humidity sensor 3a and a temperature sensor 3b are provided in the cavity 2. The casing part 1 is made of calcium sulfate dihydrate. Air 4 to be measured and in particularly its water vapor is transferred to the cavity 2 through the part 1 made of calcium sulfate dihydrate.
The humidity and temperature inside the cavity provided inside the measuring device seeks equilibrium with outside air 4. Hereby the relative humidity and temperature values measured by the humidity sensor 3a and the temperature sensor 3b located in the cavity 2 correspond to the relative humidity and temperature values of the measured air 4.
Figure 2 shows a cross-section of the temperature and humidity measuring device, in which the casing part 1, lb is different than in the figure 1. The casing part 1, lb comprises a part 1 made of calcium sulfate dihydrate and an other casing part lb. The other casing part lb is of different material than the part 1 made of calcium sulfate dihydrate. The other casing part lb may be for example substantially watertight, whereby the water vapor of the air 4 to be measured has to pass through the casing part 1 made of calcium sulfate dihydrate to enter the cavity 2.
Figure 3 shows a measuring device, which comprises a cover case 6. The measuring device is placed in an open-air space 4, which is the air to be measured. The casing part 1, lb is placed within the cover case. The cover case 6 comprises multiple air flow openings 7, through which the air to be measured can flow into the casing part 1, lb. The cover case 6 protects the casing part 1, lb from mechanical breakage. In figure 3 the casing part 1, lb comprises a part 1 made of calcium sulfate dihydrate and a casing part lb made of other material. Air flow openings 7 are provided towards the part 1 made of calcium sulfate dihydrate. If the casing part 1, lb is made largely of the part 1 made of calcium sulfate dihydrate it is preferable to provide air flow openings 7 over the entire area of the cover case 6.
In figure 3 the measuring device further comprises a radio transmitter, an antenna and a power source 5 placed in the air-filled cavity 2.
The casing part 1, lb and the cover case 6 shown in figures 1-3 are not thermally insulated, wherein the temperature of the cavity 2 settles to the ambient temperature.
The humidity sensor 3a and the temperature sensor 3b are preferably electrical sensors. Thereby the humidity sensor 3a and the temperature sensor 3b have a power supply in the cavity, for example a battery, or they are connected to a power supply outside the cavity 2. The humidity sensor 3a may be for example a capacitive humidity sensor comprising a capacitive sensing element such as for example two electrodes and a water sensitive material placed between. A sensitive material absorbs moisture from the surrounding air, which causes a change in capacitance. Capacitive humidity sensors have the advantage of their sensitivity, wide measuring range and stability. The temperature sensor 3b may be, for example, a resistance thermometer or a thermocouple.
Figure 4 shows one embodiment of the measurement device according to the present invention. The measurement device comprises a closed air-filled chamber 200. The measurement device comprises chamber walls lb defining a closed air-filled chamber space 2 inside the closed air-filled chamber 200. The chamber walls lb are provided air and water vapour impermeable such that air and water vapour may not flow through the chamber walls lb.
The chamber walls lb have an outer chamber wall surface 14 and an inner chamber wall surface 12. The inner surface defines the closed air-filled chamber space 2. The chamber walls lb comprise a flow channel 18 between the closed the closed air-filled chamber space 2 inside the closed air-filled chamber 200 and the outside of the closed air filled chamber 200, as shown in figure 4. The flow channel 18 is provided with a first barrier element 1 arranged to the flow channel 18. The first barrier element 1 blocks or closes the flow channel 18. The first barrier element 1 is arranged to define the closed air-filled chamber space 2 together with the chamber walls lb.
The first barrier element 20 comprises a first barrier inner surface 22 defining the closed air-filled chamber space 2 together with inner chamber wall surface 12 of the chamber walls lb.
The first barrier element 20 comprises a first barrier outer surface 24 defining outer surface of the closed air-filled chamber 200 together with outer chamber wall surface 14 of the chamber walls 10.
The first barrier element 1 is air and water vapour permeable enabling air and water vapour flow into and out of the closed air-filled chamber space 2 through the flow channel 18.
The measurement device further comprises a temperature sensor and humidity sensor 3a, b provided inside the air-filed chamber space 2 of the closed air-filled chamber 200.
The temperature sensor and humidity sensor 3a, b may be any know sensors.
Figure 5 shows one embodiment, comprising the closed air-filled chamber 200 of figure 4. In this embodiment, the measurement device comprises a cover case 6 surrounding the closed air-filled chamber 200. The cover case 6 encloses the closed air-filled chamber 200. The cover cas4 6 comprises an outer casing surface 44 forming the outer surface of the measurement device. The cover casing 6 also comprises inner casing surface 42 towards the closed air-filled chamber 200.
In this embodiment, the cover casing 6 is made of air and water vapour permeable material such that air and water vapour may pass through the cover casing to the flow channel 18 and further into and from the closed air-filled chamber space 2 through the first barrier element 1.
Figure 6 shows an embodiment, in which the measurement device comprises the first barrier elements 1 in the flow channel 18. The measurement device further comprises the cover casing 6 surrounding and enclosing the closed air-filled chamber 200. The cover casing 1 is made of air and water vapour impermeable material. The housing is further provided with a housing barrier element 41. The housing barrier element 41 is air and water vapour permeable and arranged to provide flow path for air and water vapour between the closed air- filled chamber 200 and outside of the cover casing 6.
The housing barrier element 41 is arranged in fluid communication with the flow channel 18 and the first barrier element 1 such that air and water vapour may flow between the outside of the cover casing 6 and the closed air-filled chamber space 2.
This first barrier element of figures 4, 5 and 6 is made of calcium sulfate dihydrate.
The watertight or air and water vapour impermeable of the chamber walls lb, or casing part lb may be polymer material, metal or the like preventing air and water vapour flow through the chamber walls lb.
In the embodiments of figures 3 and 6, the cover casing 6 is made of watertight or air and water vapour impermeable material. The watertight or air and water vapour impermeable of the cover casing 6 may be polymer material, metal or the like preventing air and water vapour flow through the chamber walls lb.
In the embodiment of figure 5, the cover casing 6 is made of air and water vapour permeable material.
The air and water vapour permeable material of the cover casing 6 is porous material for providing air and water vapour permeability. The air and water vapour permeable porous material may comprise mineral-based material, concrete, cement-based material or calcium sulfate dihydrate -based material or mixture thereof.
Similarly, the housing barrier element 41 is made of air and water permeable material, preferably porous material. The air and water vapour permeable porous material may comprise mineral-based material, concrete, cement-based material or calcium sulfate dihydrate -based material or mixture thereof.
The above description of the invention is intended only to describe the basic idea of the invention. The person skilled in the art may therefore modify its details within the scope of the accompanying claims.

Claims

1. A humidity and temperature measuring device, characterized in that the measuring device comprises a closed casing part (1, lb), an air-filled cavity (2) inside the casing part (1, lb), a humidity sensor (3a) and a temperature sensor (3b) provided in the cavity (2), the casing part (1, lb) comprises a part (1) made of calcium sulfate dihydrate, and the air (4) to be measured passes to the cavity (2) through the part (1) made of calcium sulfate dihydrate.
2. A measuring device according to claim 1, characterized in that the entire casing part (1, lb) is made of calcium sulfate dihydrate.
3. A measuring device according to claim 1, characterized in that the casing part (1, lb) comprises a part (1) made of calcium sulfate dihydrate and an other casing part, and the other casing part (lb) is substantially water tight.
4. A measuring device according to any of claims 1-3, characterized in that the part (1) made of calcium sulfate dihydrate forms a filter to the air (4) to be measured.
5. A measuring device according to any of claims 1-4, characterized in that the measuring device comprises a radio transmitter, an antenna and a power source (5) provided in the cavity (2).
6. A measuring device according to any of claims 1-5, characterized in that the measuring device comprises a cover case (6), into which the casing part (1, lb) is provided, and the cover case (6) comprises one or more air flow openings
(7).
7. A method of measuring humidity and temperature, characterized in that the method comprises a humidity and temperature measuring device according to any one of the claims 1-6 and wherein:
- a part (1) made of calcium sulfate dihydrate of the humidity and temperature measuring device is provided in contact with the air (4) to be measured, - the air to be measured flows through the part (1) made of calcium sulfate dihydrate into the cavity (2) to the humidity sensor (3a) and the temperature sensor (3b) provided in the cavity (2),
- the humidity sensor (3a) measures the relative humidity of the air and the temperature sensor (3b) measures the air temperature.
PCT/FI2020/050159 2019-03-12 2020-03-12 A humidity and temperature measuring device and method of measuring WO2020183068A1 (en)

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FI20195179A FI130572B (en) 2019-03-12 2019-03-12 Humidity and temperature measuring device, and method of measuring
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Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5879147A (en) * 1981-11-05 1983-05-12 Toshiba Corp Humidity sensitive device
CA2093196C (en) * 1992-04-10 2003-12-16 Alfred J. Hawkins Electrical sensor for sensing moisture in soils
US20090206853A1 (en) * 2007-10-05 2009-08-20 Hawkins Alfred J Sensor for sensing moisture in soils
US20100128751A1 (en) * 2007-11-28 2010-05-27 Wolfgang Doll Sensor Arrangement
CN102495112A (en) * 2011-11-11 2012-06-13 国家海洋技术中心 Intelligent air temperature/humidity measuring device
EP2510212B1 (en) * 2009-12-10 2014-11-19 Eltek S.p.A. Integrated sensor for humidity, temperature and pressure in exhaust gas
CN109814177A (en) * 2019-03-18 2019-05-28 国家海洋技术中心 A kind of temperature and humidity measuring instrument
GB2569159A (en) * 2017-12-07 2019-06-12 Climate Edge Ltd Weather station

Patent Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5879147A (en) * 1981-11-05 1983-05-12 Toshiba Corp Humidity sensitive device
CA2093196C (en) * 1992-04-10 2003-12-16 Alfred J. Hawkins Electrical sensor for sensing moisture in soils
US20090206853A1 (en) * 2007-10-05 2009-08-20 Hawkins Alfred J Sensor for sensing moisture in soils
US20100128751A1 (en) * 2007-11-28 2010-05-27 Wolfgang Doll Sensor Arrangement
EP2510212B1 (en) * 2009-12-10 2014-11-19 Eltek S.p.A. Integrated sensor for humidity, temperature and pressure in exhaust gas
CN102495112A (en) * 2011-11-11 2012-06-13 国家海洋技术中心 Intelligent air temperature/humidity measuring device
GB2569159A (en) * 2017-12-07 2019-06-12 Climate Edge Ltd Weather station
CN109814177A (en) * 2019-03-18 2019-05-28 国家海洋技术中心 A kind of temperature and humidity measuring instrument

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