Vaisala Humidity 101 - Humidity Sensor Technology Tutorial

WelcomeVaisala Humidity 101 – Humidity Sensor Technology - TutorialBruce McDuffee Yumi Shakya Vaisala Humidity Vaisala Application Instructor EngineerHumidity 101 \ webinar seriesHumidity Sensor Technology - TutorialƒƒƒƒƒƒAgenda 1. Sensor TechnologiesMechanical/OrganicPsychrometersChilled mirrorElectronic® 2. Vaisala HUMICAP TrainingHeated probeChemical purge® 3. Vaisala DRYCAP TrainingPage 3 / 11/10/08 / BEMD / ©Vaisala MechanicalExploit the expansion and contraction of organic materials with changes in humidity; changes are amplified through the use of levers that move a needle or pointer.• horse hair, human hair, catgut, goldbeater’s skin, textile, or plastichair elementPage 4 / 11/10/08 / BEMD / ©Vaisala Mechanical+ cheap to buy+ no power needed- 20…90% best range- Uncertainty from +/-5% up to +/-15%- calibrated with a wet rag to 100%; no dry end calibration- considerable hysteresis- responds to changes in humidity very slowlyhair elementPage 5 / 11/10/08 / BEMD / ©Vaisala Psychrometer (wet-dry bulb)Two matched thermometers over which air is drawn. One thermometer has the bulb covered by a wet ‘cloth’ or ‘wick’. This is the ‘wet-bulb’.dry bulbclothwet bulbwaterPage 6 / 11/10/08 / BEMD / ©Vaisala Psychrometer (wet-dry bulb)- High uncertainty (+/- 2% to 5%)+ simple & fundamental measurement- requires some skill to use & maintain+ relatively cheap ($35 to $80 for sling)- results usually must be calculated+ can ...