Editing Water vapor (section)

=== Measurement ===
Measuring the quantity of water vapor in a medium can be done directly or remotely with varying degrees of accuracy. Remote methods such [[Electromagnetic absorption by water|electromagnetic absorption]] are possible from satellites above planetary atmospheres. Direct methods may use electronic transducers, moistened thermometers or hygroscopic materials measuring changes in physical properties or dimensions.

{| class="wikitable sortable" style="text-align: center; font-size: 85%; width: auto; table-layout: fixed;"
|-
! style="width:12em" |
! medium
! temperature range (degC)
! measurement [[Measurement uncertainty|uncertainty]]
! typical measurement frequency
! system cost
! notes
|-
! style="text-align:left;"| [[Hygrometer#Sling psychrometer|Sling psychrometer]]
| air
| −10 to 50
| low to moderate
| hourly
| low
|
|-
! style="text-align:left;"| Satellite-based spectroscopy
| air
| −80 to 60
| low
|
| very high
|
|-
! style="text-align:left;"| [[Hygrometer#Capacitive|Capacitive]] sensor
| air/gases
| −40 to 50
| moderate
| 2 to 0.05&nbsp;Hz
| medium
| prone to becoming saturated/contaminated over time
|-
! style="text-align:left;"| Warmed capacitive sensor
| air/gases
| −15 to 50
| moderate to low
| 2 to 0.05&nbsp;Hz (temp dependant)
| medium to high
| prone to becoming saturated/contaminated over time
|-
! style="text-align:left;"| [[hygrometer#Resistive|Resistive]] sensor
| air/gases
| −10 to 50
| moderate
| 60 seconds
| medium
| prone to contamination
|-
! style="text-align:left;"| Lithium chloride [[dewcell]]
| air
| −30 to 50
| moderate
| continuous
| medium
| see [[dewcell]]
|-
! style="text-align:left;"| [[Cobalt(II) chloride]]
| air/gases
| 0 to 50
| high
| 5 minutes
| very low
| often used in [[Humidity indicator card]]
|-
! style="text-align:left;"| [[Absorption spectroscopy]]
| air/gases
|
| moderate
|
| high
|
|-
! style="text-align:left;"| Aluminum oxide
| air/gases
|
| moderate
|
| medium
| see [[Moisture analysis]]
|-
! style="text-align:left;"| Silicon oxide
| air/gases
|
| moderate
|
| medium
| see [[Moisture analysis]]
|-
! style="text-align:left;"| Piezoelectric sorption
| air/gases
|
| moderate
|
| medium
| see [[Moisture analysis]]
|-
! style="text-align:left;"| Electrolytic
| air/gases
|
| moderate
|
| medium
| see [[Moisture analysis]]
|-
! style="text-align:left;"| [[Hygrometer#Hair tension hygrometers|Hair tension]]
| air
| 0 to 40
| high
| continuous
| low to medium
| Affected by temperature. Adversely affected by prolonged high concentrations
|-
! style="text-align:left;"| Nephelometer
| air/other gases
|
| low
|
| very high
|
|-
! style="text-align:left;"| [[Goldbeater's skin]] (Cow Peritoneum)
| air
| −20 to 30
| moderate (with corrections)
| slow, slower at lower temperatures
| low
| ref:WMO Guide to Meteorological Instruments and Methods of Observation No. 8 2006, (pages 1.12–1)
|-
! style="text-align:left;"| Lyman-alpha
|
|
|
| high frequency
| high
| http://amsglossary.allenpress.com/glossary/search?id=lyman-alpha-hygrometer1 Requires frequent calibration
|-
! style="text-align:left;"| [[hygrometer#Gravimetric|Gravimetric]] Hygrometer
|
|
| very low
|
| very high
| often called primary source, national independent standards developed in US, UK, EU & Japan
|- class="sortbottom"
!
! medium
! temperature range (degC)
! measurement [[Measurement uncertainty|uncertainty]]
! typical measurement frequency
! system cost
! notes
|}