ECE5320 Mechatronics Assignment#01: Literature Survey on Sensors and Actuators Topic: Humidity SensorOutlineReference listTo Explore FurtherAbout HumidityCalculating HumidityMajor applicationsMeasuring MethodsMethods (cont. )CapacitiveApplication NotesResistiveThermal ConductiveThermal Sensor PropertiesTypical ConfigurationApplication Notes (cont.)SpecificationsCondensationMethod for CalibrationSalt Solutions and MethodECE5320 MechatronicsAssignment#01: Literature Survey on Sensors and Actuators Assignment#01: Literature Survey on Sensors and Actuators Topic: Humidity SensorPrepared by:Roger PackhamDept. of Electrical and Computer Engineering Utah State UniversityE: [email protected] ; F: (435)797-3054 (ECE Dept.)W: http://cc.usu.edu/~rpackham 3/11/200501/14/19ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuatorsSlide-2Outline –Reference list–To probe further–About Humidity–Major applications–Basic working principle illustrated–A typical sample configuration in application (application notes)–Major specifications–Limitations–Relevant issues in applications (such as, how to choose, cost information, calibration.)01/14/19ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuatorsSlide-3Reference list•Smartec - http://www.smartec.nl/•Inexpensive analog sensor, useful application tools and information.•Humirel - http://www.humirel.com/•Variety of analog and digital output sensors.•Honeywell - http://content.honeywell.com/sensing/prodinfo/humiditymoisture/ •Good technical documentation and high quality sensors.•Sensirion - http://www.sensirion.com/en/sensors/humidity/default.htm •Compact digital output sensor packages.•Clark Solutions - http://www.clarksol.com/html/prodspecsFNA.htm •Handheld pshychrometric temperature and humidity units.•Sensor Magazine - http://www.sensorsmag.com/articles/0701/54/main.shtml Note: Pictures have origin noted in the properties window01/14/19ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuatorsSlide-4To Explore Further •Honeywell -provides many specific details and test data for their capacitive humidity sensors. http://content.honeywell.com/sensing/prodinfo/humiditymoisture/ •Sensor Magazine article discusses resistive and thermal sensors in depth. Useful article on choosing humidity sensor technology and devices. http://www.sensorsmag.com/articles/0701/54/main.shtml•Sensor Magazine article documents a one-wire miniature weather station. http://www.sensorsmag.com/articles/0800/62/index.htm01/14/19ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuatorsSlide-5About HumidityTerm Definition Unit (IS) CommentMixing RatioMass, Water vaporMass, Dry airkg/kgalso in g/kg orlb/lbAbsolute HumidityMass, Water vaporVolume,kg/m3also in g/m3 orgrains/ft3RELATIVE HUMIDITYActual water vapor pressureSaturation water vapor pressure%Can be also the masse ratio.Dew PointTemperature of condensation(saturation)K also °C or °F RELATIVE HUMIDITY (%RH) is most commonly used.http://www.humirel.com/All_about_humidity.htm01/14/19ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuatorsSlide-6Calculating Humidity•The RELATIVE HUMIDITY is defined as the ratio of the partial pressure vapor to saturation vapor pressure at a given temperature. By measuring the relative humidity, we compare the actual quantity of water vapor to the maximum quantity of water vapor which can be found in these conditions of ambient temperature and pressure. DEW POINT is the temperature at which the wet gaseous atmosphere can not be held in equilibrium in its gaseous form only. It will characterized by the emergence of a liquid phase. ABSOLUTE HUMIDITY is the water vapor concentration in the air. This concentration value is either linked with the volume (in kg/m3, or g/m3 or grains/ft3) or linked with the mass (in kg/kg or g/kg or lb/lb). In the latter case, it will be named the MIXING RATIO. •Using the AMBIENT TEMPERATURE and one of the above three values, the other two can be calculated.http://www.humirel.com/All_about_humidity.htm01/14/19ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuatorsSlide-7Major applications •Office automation, room comfort control •Automotive cabin air control•Home appliances, Air conditioners •Industrial process control systems. Storage and warehouses •Climate control for green houses •Meteorological applications •Food processing •Medical applications •Chicken Coops, Pig Barns01/14/19ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuatorsSlide-8Measuring Methods•Capacitive - absorption of water into dielectric.–Small, dependable–Accurate over wide temperature range without compensation.•Resistive - measure the change in electrical impedance of a hygroscopic medium such as a conductive polymer, salt, or treated substrate.01/14/19ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuatorsSlide-9Methods (cont. )•Thermal Conductive - measure the absolute humidity by quantifying the difference between the thermal conductivity of dry air and that of air containing water vapor. •Psychrometric - cotton wicks water to make a wet bulb temperature sensor. An internal fan blows air across the wet bulb sensor, causing the moisture to evaporate, cooling the sensor in contrast to the dry one. –Handheld units.–Time tested, measure multiple ambient statistics at once.01/14/19ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuatorsSlide-10Capacitive•Capacitance increases in value as water molecules are absorbed into its active polymer dielectric. The capacitor plates consists of a base plate and a water permeable platinum top plate. Polymers give protection to the base plate. • Substrate can include signal conditioning circuitry to produce a linear output, or a digital interface.• Thermoset-polymer (faster, more robust) or Thermoplastic• $10 to $6801/14/19ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuatorsSlide-11Application Notes•Special attention is required in order to minimize stray capacitance in the layout. The added capacitance will act as a parallel capacitance with the sensor and create a measurement error (+/- 6% with +25pF).•Capacitive sensors are limited by the distance the sensing element can be located from the signal conditioning circuitry, due to the capacitive effect of the connecting cable with respect to the relatively small capacitance changes of
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