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Sensor Calibration and Quality Assurance Procedures
Relative Humidity
Equipment:
- Rotronic MP101A Humidity Temperature Probe S/N 90768
- NOAA Humidity and Temperature Sensors
- Compact Sling Psychrometer
Procedure:
NOAA has a suite of meteorological sensors established at the Bodega Marine Reserve. Data from these sensors can be downloaded from the internet at http://www.etl.noaa.gov/et7/data/archive/UneditedActive/.
These data are used for sensor comparison by downloading a data set from an entire day.
Since NOAA data are logged at two minute intervals, BML data are also selected at two minute increments, but data are not averaged to determine the two minute mean of the 10 second data points. They are simply instantaneous values recorded every two minutes.
Sample Relative Humidity Comparison
The two independent data sets are compared graphically in Matlab to look for general agreement. Any gross differences are investigated further. An average difference between the values measured by the two sensors is also calculated.
BML relative humidity measurements are considered good if the two data sets agree within 5%. Relative humidity is also checked periodically with a sling psychrometer. Though the psychrometer does not have the degree of precision of the Rotronic probe, it is a simple single point check.
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