FAWN Measurement System Specifications

Tower

Equipment Manufacturer Model
Tower Campbell Scientific UT20 (Hinged for lowering)
Electronics Enclosure Campbell Scientific ENC16/18
Solar Panel Campbell Scientific ()BP Solar) SP20
Solar Controller Morningstar Sunguard-SG4

Measurements

Measurement Sensor Type Manufacturer Model Number Units
(reported)		 Sampling
Frequency/rate		 Reporting
Frequency
Temperature - Soil Thermistor Campbell Scientific 107-l Celsius 5 seconds 15 Minutes
Temperature - Air
(60 cm)		 Thermistor Campbell Scientific 107-l Celsius 15 seconds 15 Minutes
Temperature - Air
(2 m)		 Bandgap Campbell Scientific CS215 Celsius 15 seconds 15 Minutes
Temperature - Air
(10 m)		 Thermistor Campbell Scientific 107-l Celsius 15 seconds 15 Minutes
Relative Humidity Capacitive Campbell Scientific CS215 Percent 5 seconds 15 Minutes
Rainfall Tipping Bucket   H-340 Inches .01 inch 15 Minutes
Barometric Pressure Capacitive Campbell Scientific CS105 Millibars 5 seconds 15 Minutes
Solar Radiation Silicon Photovoltaic Campbell Scientific LI200X Watts per square meter 5 seconds 15 Minutes
Wind Speed Ultrasonic Vaisala 425A Miles per hour 5 seconds 15 Minutes
Wind Direction Ultrasonic Vaisala 425A Degrees N/A 15 Minutes
Temperature - Dew Point
(2m)		 Calculated* N/A N/A Celsius N/A 15 Minutes
Temperature - Wet Bulb (2m) Calculated* N/A N/A Celsius N/A 15 Minutes
Evapotranspiration (ET) Calculated* N/A N/A Inches per day N/A 24 Hours 
      *Measurement - Calculated

      
Temperature - Dew Point (2m):


        Td = 243 * ln(e / 6.112) / 17.67 - ln(e / 6.112)

        where:
        		
          Td = Dew Point Temperature (2m)

          e = Vapor Pressure = relative humidity / 100 * es

        and

          es = Saturation Vapor Pressure =  6.112 * exp(17.67 * T / (T + 243.5))

          T = Temperature (2m)

      
Temperature - Wet Bulb (2m) - calculated by using Newton-Raphson algorithm:


        Tw= es- 0.000666 * P * (T -Two) - Td
         
        where: 

          es= Saturated Vapor Pressure

          P = Station Pressure

          T = Air Temperature (2m)

          Two= Wet Bulb Temperature (from previous iteration, 0 in first iteration)

          Td= Dew Point Temperature (2m)

        References:
      http://mysite.du.edu/~etuttle/weather/atphys.htm
      http://en.wikipedia.org/wiki/Newton%27s_method

      
Evapotranspiration: FAO Penman-Monteith.


      et
      et_2

      Reference:  
      http://ufdcimages.uflib.ufl.edu/UF/E0/00/73/60/00001/mitchell_m.pdf

Data Storage

  • Equipment: Data Logger
  • Manufacturer - Campbell Scientific
  • Model - CR10X

Communication

Equipment Manufacturer Model
Radio (local Intranet) Campbell Scientific RF401
Modem (local Intranet) Campbell Scientific NL100
Modem (cellular) Campbell Scientific Raven Edge

Data Quality Control

Range check: to ensure each measurement is within the following acceptable range
Measurement Minimum Value Maximum Value
All Temperature (C) -20 50
Relative Humidity (%) 0 100
Barometric Pressure (mb) 940 1060
Rain (in) 0 3
Solar Radiation (W/m2) 0 1200
Wind Speed (mph) 0 75
Wind Direction (deg) 0 360
Step Check: to ensure current measurements are consistent with those measured at previous time
Measurement Time Step (Hours) Threshold
All Temperature (C) 1 10
Barometric Pressure (mb) 3 6