Campbell-scientific 109SS Temperature Probe Manual de usuario descargar pdf (Pagina 24)

Appendix B. Example Programs

'*AG = Analog Ground (represented by ground symbol on CR1000 wiring panel

'Declare the variables for the temperature measurement

Public T109_C

'Define a data table for 60 minute averages

DataTable(Table1,True,-1)

DataInterval(0,10,Min,10)

Average(1,T109_C,FP2,False)

EndTable

'Main Program

BeginProg

Scan(1,Sec,1,0)

'Measure the temperature

Therm109(T109_C,1,1,1,0,_60Hz,1.0,0)

'Call Data Table

CallTable(Table1)

NextScan

EndProg

B.1.3 Example 3 — Sample Program using the BrHalf()

instruction rather than Therm109()

‘Program measures a single 109 Thermistor probe once a second and

‘stores the average temperature every 60 minutes.

'Wiring Diagram

'==============

'109SS Probe

' Wire

' Color Function CR1000

' ----- -------- ------

' Black Voltage-excitation input VX1 or EX1

' Red Analog-voltage output SE1

' Purple Bridge-resistor ground AG*

' Clear Shield G*

'*AG = Analog Ground (represented by ground symbol on CR1000 wiring panel

'Declare the variables for the temperature measurement

Public T109_C

'Declare variables for the raw measurement, thermistor resistance,

‘and ln(resistance):

Dim V_Vx, Rtherm, lnRt

'Define a data table for 60 minute averages

DataTable(Table1,True,-1)

DataInterval(0,10,Min,10)

Average(1,T109_C,IEEE4,False)

EndTable

BeginProg

Scan (1,sec,5,0)

'Measure the 109SS probe. The result is V/Vx.

BrHalf (V_Vx,1,mV5000,3,Vx1,1,5000,True,0,_60Hz,1.0,0)

'Calculate reistance:

RTherm=24900*(1/V_Vx-1)

'Calculate the natural log of the resistance

lnRt=Log(Rtherm)

'Apply the Steinhart-Hart equation and convert to degrees C in one step:

Air_Temp=1/(1.129241e-3+2.341077e-4*lnRt+8.775468e-8*(lnRt^3))-273.15

B-2

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Campbell-scientific 109SS Temperature Probe Manual de usuario Pagina 24

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