Campbell Scientific 110PV Surface Temperature Probe - Manual (Page 18)

110PV Surface Temperature Probe
5.1.1.1 Sample Program for CR200(X) Series Datalogger
'CR200 Series Datalogger
'This example program measures a single 110PV-L probe
'once a second using the ExDelSE instruction and stores
'the average temperature in degrees C every 10 minutes.
'110PV-L Wiring configuration for program example
'Lead Color CR200(X) Channel Description
'Black ------ VX1 ------------ Voltage Excitation
'Red -------- SE1------------- Signal
'Purple----- AG-------------- Signal Reference
'Blue ------- Not Used ------ N/A
'Green ----- Not Used ------ N/A
'White------ Not Used ------ N/A
'Clear ------ AG-------------- Shield
'Declare variables for temperature measurement
Public T110PV_mV
Public T110PV_Res
Public T110PV_Temp_C
Public T110PV_Temp_F
'Declare constants to be used in Steinhart-Hart equation
Const A=1.129241*10^-3
Const B=2.341077*10^-4
Const C=8.775468*10^-8
Const R_cable=0
'see sensor cable for cable resistance
'Declare variable units
Units T110PV_mV= millivolts
Units T110PV_Res=Ohms
Units T110PV_Temp_C=Deg C
'Define a data table for 10 minute averages
DataTable (AvgTemp,1,1000)
DataInterval (0,10,min)
Average (1,T110PV_Temp_C,False)
EndTable
'Main Program
BeginProg
Scan (1,Sec)
' Measure 110PV-L probe with SE1
ExDelSE (T110PV_mV,1,1,Ex1,mV2500,500,1.0,0)
' Convert mV to ohms
T110PV_Res = 4990*(2500/T110PV_mV)-4990
' Subtract off cable resistance (see 110PV-L cable for R_cable)
T110PV_Res = T110PV_Res-R_cable
' Using the Steinhart-Hart equation to convert resistance to temperature
T110PV_Temp_C = (1/(A+B*LOG(T110PV_Res)+C*(LOG(T110PV_Res))^3))-273.15
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