Vaisala Humidity 101 - Humidity Sensor Technology Tutorial

Bruce Mcduffee

Description

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 ...

Informations

• Publié par: Uste
• Nombre de lectures: 76
• Langue: English

Extrait

Welcome

Vaisala Humidity 101 – Humidity Sensor Technology - Tutorial

Bruce McDuffee Vaisala Humidity Instructor

Yumi Shakya Vaisala Application Engineer

Humidity 101 \ webinar series

Humidity Sensor Technology - Tutorial

Agenda

1.

2.

3.

Sensor Technologies ƒMechanical/Organic ƒsychPtersrome ƒChilled mirror ƒElectronic

Vaisala HUMICAP ® Training ƒHeated probe ƒChemical purge

Vaisala DRYCAP ® Training

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Mechanical

Exploit 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.

•hair, catgut, goldbeater’s skin, textile, or plastichorse hair, human

hair element

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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 slowly

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hair element

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 bulb

wet bulb

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cloth

water

+simple & fundamental measurement +relatively cheap ($35 to $80 for sling) +can have good stability +tolerates condensation without damage

1 fa n m o tor he a t intro duc e d 5 p oor w a te r q ua lity 2 turbula nc e w a te r te m pe ra ture c ha ng e s a ffe c t d e p re ssion 3 thic k w ic k 6 w a te r c o nta ine r m a te ria l non- pla stic c onta m ina te d w ic k 7 tw o- w ire sy ste m c a use s e rro rs w ic k q ua lity 8 ta ble s, a c c ura c y o f re a d ing po rous ( c e ra m ic ) sle e v e 4 no n- se a le d the rm om e te rs no n- id e ntic a l the rm o m e te rs po or re solution instrum e nts low a c c ura c y instrum e nts

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5

6

7 TA BLES

1 2  4 HY G RO M ETER 3

Psychrometer (wet-dry bulb)

8

uqerserimos ks el il uto &seai m gi hnuectriatn y(+/- 2% to 5%) -   H- sie avopret ah t ) by  wat (alteredfidi deieb lmuh lempil w lemp sa-   ras eiaalgrer sequi d - r latealcuc eb tsum yllaus utsules r n - aint E H UR ROYGTRMEIC NESOLC wickanetatimtr y/did teecff a on   c byd  - gnitar ycarucca

Condensation Hygrometer

Chilled Mirror

ligh t

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N O D E W

c h ille d m irro r

d e te c to r

lig h t

D E W

c h ille d m irro r

to r

Condensation Hygrometer

+precise measurement (+/-.1C) +wide measurement range (-100..+100C) +very good long term performance   fundamental measurement +

expensive

- -usually requires some skill/training to operate -mirror cannot tell ice or dew -contamination on mirror causes errors -requires frequent maintenance -complex in construction

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Electrical Sensors

Resistive

Capacitive – thin film polymer

Capacitive – aluminum oxide

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Resistive Humidity Sensors

Measures the electrical impedance or resistance of a hygroscopic medium such as conductive polymer, salt, or a treated substrate.

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The resistance changes inversely with humidity.