Calculation Notes

Last modified by Michael Sibayan on 2014/11/14 09:01
Sensor Code:5TM
Sensor:5TM from Decagon Devices Inc.
Measurement:Volumetric water content (%) and Temperature (°C)
Output 1:Apparent dielectric permittivity (unit-less)Range 1:1 to 80
Output 2:Temperature (°C)Range 2:-40 to 50
Output 3:VWC (\%) = 17.8 * \sqrt{output1} - 40.9 Range 3:0 to 50

C8 soil calibration as provided by Decagon Devices on August 15, 2011.  Database uses coefficients A=17.8, B=40.9

Sensor Code:MPS-2
Sensor:MPS-2 from Decagon Devices Inc.
Measurement:Matric soil potential (kPa) and Temperature (°C)
Output 1:Matric soil potential (kPa)Range 1:-5 to -500
Output 2:Temperature (°C)Range 2:-40 to 50
Sensor Code:TCAV
Sensor:TCAV from Campbell Scientific Inc.
Measurement:Spatial average temperature (°C)
Output 1:Temperature (°C)Range 1:-40 to 50
Sensor Code:HFP-1 & HFP-1SC
Sensor:HFP-1 & HFP-1SC from Hukseflux Inc.
Measurement:Heat flux (Watts / m2)
Output 1:VoltsRange 1:-0.1 to 0.1
Output 2:Flux (\frac{W}{m^2}) = output1 * \frac{1000000}{k}Range 2:-2000 to 2000

Each sensor has its own calibration coefficient (k), see database. k is nominally 50μV / W / m
SC version of this sensor has control for an internal heater

Sensor Code:GMM222
Sensor:GMM222 from Vaisala Inc.
Measurement:CO2 Concentration (ppm)
Output 1:VoltsRange 1:0 to 2.5
Output 2:Concentration (ppm) = \frac{output1*k}{2.5}Range 2:0 to 5000, 0 to 7000 (depending on range)

k is either 5000ppm or 7000ppm

Sensor Code:Model3130
Sensor:Model3130 from Honeywell International Inc.
Measurement:Force (converted to mass in kg)
Output 1:mV/V (unit-less)Range 1:-0.003 to 0.003
Output 2:Mass (kg) = Output1*\frac{{MaxLoad} * {453.59236}}{k}Range 2:0 to 2*108

Calibration coefficient, k, is the output at the rated MaxLoad (kip). For mass calculations: m=F/a, where a is 9.80665 (gravity) and 1 kip = 4448.2216 newtons (N)

Sensor Code:Model41
Sensor:Model41 from Honeywell International Inc.
Measurement:Force (converted to mass in kg)
Output 1:mV/V (unit-less)Range 1:-0.003 to 0.003
Output 2:Mass (kg) = Output1*\frac{{MaxLoad} * {0.45359}}{k}Range 2:0 to 2*108

Calibration coefficient, k, is the output at the rated MaxLoad (lbs). The calibration parameters are provided to calculate lbs, therefore the conversion to kg requires 0.45359

Sensor Code:EX81
Sensor:EX81P from Seametrics Inc.
Measurement:Volume of flow
Output 1:Pulses (unit count)Range 1:0 to 1000000
Output 2:Volume (L) = \frac{output1}{k} * 3.78541178Range 2:0 to ?
Sensor Code:PE102
Sensor:PE102 from Seametrics Inc.
Measurement:Volume of flow (Liters)
Output 1:Pulses (unit count)Range 1:0 to 600000
Output 2:Volume (L) = \frac{output1}{k}Range 2:0 to ?

For the "-075" model, k = 500 pulses per liter. For the low flow "-032" model, k = 1000 pulses per liter.

Sensor Code:NovaLynx
Sensor:260-2501-A  from NovaLynx
Measurement:Volume of flow (Liters)
Output 1:Pulses (unit count)Range 1:0 to 60 (per minute)
Output 2:Volume (L) = {output1}*{k}Range 2:0 to ?

The rain gauge is designed to measure inches of rain at 0.01” per tip. When used as a flow meter, each tip corresponds to a specific volume of water. With an 8” input area this equates to 0.5024 cu. in. or 0.008237 liters of water.

k (rainfall) = 0.01”/tip,  k (volume) = 0.008237 liters/tip

The calibration parameter, k, is determined empirically.

Sensor Code:TB
Sensor:Any valid tipping bucket flow meter
Measurement:Volume of flow (Liters)
Output 1:Pulses (unit count)Range 1:Unspecified
Output 2:Volume (L) = {output1}*{k}Range 2:Unspecified

The rain gauge tipping bucket is designed to measure height of rain per tip. When used as a flow meter, each tip corresponds to a specific volume of water. 

The calibration parameter, k, is determined empirically.

Sensor Code:PTB110
Sensor:PTB110 from Vaisala
Measurement:Barometric pressure (hPa)
Output 1:VoltsRange 1:0 to 2.5
Output 2:Pressure (hPa) = \frac{output1}{vmax}*(pmax-pmin)+pminRange 2:500 to 1100

pmax and pmin refer to the range of the sensor. Vmax is the voltage at maximum calibrated pressure.

Sensor Code:DeviceT
Sensor:Onboard temperature measurement of any device given in degrees Celsius
Measurement:Temperature (C)
Output 1:Temperature (C)Range 1:unspecified
Sensor Code:TC-x
Sensor:Thermocouple of type “x” where “x” is any valid thermocouple type (E.g. E,K,T,…)
Measurement:Temperature (C)
Output 1:Temperature (C)Range 1:unspecified
Sensor Code:Model81000VRE
Sensor:Model 81000VRE from Young Company
Measurement:Wind velocity and air characteristics
Output 1:Speed (m/s) – air speedRange 1:0 to 40
Output 2:Angle (degrees) -- directionRange 2:0 to 360
Output 3:Angle (degrees) -- elevationRange 3:-60 to +60
Output 4:Speed (m/s) – speed of soundRange 4:300 to 360
Output 5:Temperature (C)Range 5:-50 to 50
Sensor Code:CSAT3
Sensor:CSAT3 from Campbell Scientific
Measurement:Three component wind velocity and speed of sound
Output 1:Ux (m/s) – air speedRange 1:-65.5 to 65.5
Output 2:Ux (m/s) – air speedRange 2:-65.5 to 65.5
Output 3:Ux (m/s) – air speedRange 3:-65.5 to 65.5
Output 4:Speed (m/s) – speed of soundRange 4:300 to 366
Sensor Code:HMP60
Sensor:HMP60 from Vaisala (sold by Campbell Scientific)
Measurement:Relative Humidity, Temperature
Output 1:VoltsRange 1:0 to 1
Output 2:VoltsRange 2:0 to 1
Output 3:Relative Humidity (%) = Output1 * 10Range 3:0 to 100%
Output 4:Temperature (C) = Output2 * 100 - 40Range 4:-40 to +60
Sensor Code:DVI7911
Sensor:DVI7911 from Davis Instruments
Measurement:Wind velocity and direction
Output 1:Pulse countRange 1:unspecified
Output 2:V/V (unit-less)Range 2:0 to 1
Output 3:Average speed (m/s) = Output1 * k / TRange 3:unspecified
Output 4:Direction (degrees) = Output2 * 360Range 4:0 to 360
Sensor Code:SQ-110
Sensor:SQ-110 from Apogee
Measurement:Photosynthetic photon flux
Output 1:Volts
Range 1:0 to 0.8
Output 2:photon flux (µmol * m-2 * s-1) = Output1 * k
Range 2:0 to 4000
Sensor Code:CS451
Sensor:CS451 from Campbell Scientific
Measurement:Pressure (water level)
Output 1:Pressure (PSI)Range 1:0 to 2.9
Output 2:Temperature (C)Range 2:0 to 60
Output 3:Water level (cmH2O) = Output1 * 70.307 + offsetRange 3:0 to 200

The value of "offset" is determined empirically

Sensor Code:T4 / T4E
Sensor:T4 / T4E from Umwelt Monitoring Systems (UMS)
Measurement:Soil water tension
Output 1:VoltsRange 1:-0.1 to 0.085
Output 2:Tension (kPa) = Output1 * (-1000) + offsetRange 2:-85 to 100
Sensor Code:CNR4
Sensor:CNR4 from Kipp-Zonen (sold by Campbell Scientific)
Measurement:Global and reflected radiation intensity
Output 1:VoltsRange 1:0 to 0.015
Output 2:VoltsRange 2:0 to 0.015
Output 3:VoltsRange 3:-0.005 to 0.005
Output 4:VoltsRange 4:-0.005 to 0.005
Output 5:ResistanceRange 5:80 to 130
Output 6:Incoming shortwave intensity (Watts/m^2) = \frac{Output1}{ka}*1000000Range 6:0 to 1000
Output 7:Outgoing shortwave Intensity (Watts/m^2) = \frac{Output2}{kb}*1000000Range 7:0 to 400
Output 8:Temperature (K) = \frac{-a+\sqrt{a^2-4b(1-\frac{Output5}{Ro})}}{2b}+273.15Range 8:220 to 335
Output 9:Incoming long wave intensity (Watts/m^2) = \frac{Output3}{kc}*1000000 + (5.67 * 10^{-8} * output8^4) Range 9:-150 to 0
Output 10:Outgoing long wave intensity (Watts/m^2) = \frac{Output4}{kc}*1000000 + (5.67 * 10^{-8} * output8^4)  Range 10:-25 to 25

ka, kb, kc, and kd are the four calibration coefficients assumed to be in microvolts per W/m^2

Pt-100 RTD has a temperature relation approximated by theCallendar-Van Dusen equation. A =3.908x10^-3; B = -5.8019*10^-7; C = -4.2735*10^-12; Ro = 100; for the DIN standard RTD used in the CNR4.
Temperature formula is only valid for T > 272.15 (K)
A numeric approximation is used for T < 272.15 (K)

Sensor Code:VW-PZO
Sensor:GEO-VW-PZO from Geo-Instruments LLC
Measurement:Pressure (PSI - converted to cmH2O)
Output 1:Frequency (Hz)Range 1:2000 to 6000
Output 2:Resistance (ohm)Range 2:2000 to 4000
Output 3:Pressure (cm H2O)Range 3:0 to 120

The calculations required to determine pressure are as follows:

D1=\frac{Output1^2}{1000}
D0=\frac{(F0)^2}{1000}
T0=\frac{1}{(D+(E*Ln(R0)+F*(Ln(R0))^3 ))}-273.15
T1=\frac{1}{(D+(E*Ln(Output2)+F*(LN(Output2))^3)}-273.15
P(cmH20)=(A*(D1^2-D0^2)+ B*(D1-D0)+K*(T1-T0))* 70.3089

Sensor Code:WTW340
Sensor:WTW340 from WTW
Measurement:Electrical conductivity (µS/cm) 
Output 1:VoltageRange 1:0 to 5
Output 2:Conductivity (micro-siemens / cm)Range 2:Unspecified
Sensor Code:VALWORX
Sensor:VALWORX Ball Valve
Measurement:Valve state
Output 1:Valve StateRange 1:1, 0, -1, -9999

The valve contains two SPST-NO relays. One relay is used to indicate an open valve, and the other is used to indicate a closed valve.
The output logged to the database is determined by the table below.

Open RelayClosed RelayIndicated State 
0 (Low)0 (Low)0 (Unknown/Transition)
1 (High)0 (Low)1 (Open) 
0 (Low)1 (High) -1 (Closed)
1 (High)1 (High)-9999 (Inconsistent) 
Sensor Code:LI7000
Sensor:LI-COR LI-7000
Measurement:CO2 & H2O concentration
Output 1:Cell A CO2 Concentration (umol/mol)Range 1:0-3000
Output 2:Cell B CO2 Concentration (umol/mol)Range 1:0-3000
Output 3:Cell A H2O Concentration (mmol/mol)Range 2:0-60
Output 4:Cell B H2O Concentration (mmol/mol)Range 1:0-60
Output 5:Cell B Pressure (kPa)Range 1:0-115
Output 6:IRGA Temperature (C)Range 1:0-3000
Sensor Code:SurfaceHeatFlux
Sensor:Computed data from 5TM, TCAV, and HFP-1/SC
Measurement:Heat flux (Watts / m2)
Output 1:Heat flux at surface for HFP-1 (Watts/m2)Range 1:-2000 to 2000
Output 2:Heat flux at surface for HFP-1SC (Watts/m2)Range 2:-2000 to 2000
Output 3:Average surface heat flux (Watts/m2)Range 3:-2000 to 2000

Moist soil heat capacity:  C_s (kJ/m^3/k) = \rho_b * C_d +  \rho_w * \theta_v * C_w

\rho_b = bulk density (For LEO this is  1570 kg/m3)
\rho_w = density of water (999 kg/m^3)
\theta_v = the volumetric water content (decimal 0.0 to 0.5)
Cd = heat capacity of dry soil (0.89 kJ/kg/K)
Cw = heat capacity of water (4.179 kJ/kg/K)

Storage term S (W/m^2) = (\Delta T_s * C_s * d) / t
\Delta T_s = change in soil temperature  
d = depth
t = output interval

Soil heat flux at the surface, G_{sfc} = G_{8cm} + S

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Created by Michael Sibayan on 2014/11/14 09:04

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