Section 7. Installation
299
CRBasic Programs and Notes
PT100 Resistance() Four-Wire Full-Bridge Calibration
'This program example demonstrates the calibration of a 100-ohm PRT (PT100) in a four-wire
'full bridge with current excitation. See previous procedure and schematic
'
'Declare constants and variables:
Const
R1 = 5000000
'Value of R1 bridge resistor
Const
R2 = 120000
'Value of R2 bridge resistor
Const
R4 = 5000000
'Value of R4 bridge resistor
Public
X
'Raw output from bridge
Public
RS0
'Calculated PT100 resistance at 0 °C
BeginProg
Scan
(1,Sec,0,0)
'Measure X
'Resistance(Dest,Reps,Range,InputChan,IExChan,MPE,ExuA,RevEx,RevDiff,
' SetttlingTime,
Integ
,Mult,Offset)
Resistance
(X,1,mV50,1,Ix1,1,2,True,True,0,250,1,0)
'Calculate RS0:
RS0 = ((-R2*R4) - (X*(R1+R2+R4))) / (X-R1)
NextScan
EndProg
PT100 Resistance() Four-Wire Full-Bridge Measurement
'This program example demonstrates the measurement of a 100-ohm PRT (PT100) in a four-wire
'full bridge with current excitation. See previous procedure and schematic.
'
'Declare constants and variables:
Const
R1 = 5000000
'Value of R1 bridge resistor
Const
R2 = 120000
'Value of R2 bridge resistor
Const
R4 = 5000000
'Value of R4 bridge resistor
Const
RS0 = 100000
'Resistance of PT100 at 0 °C from calibration program
Public
X
'Raw output from bridge
Public
RS
'Calculated PT100 resistance
Public
RS_RS0
'Calculate ratio of RS/RS0
Public
DegC
'Calculated temperature of PT100
BeginProg
Scan
(1,Sec,0,0)
'Measure X
'Resistance(Dest,Reps,Range,InputChan,IExChan,MeasPEx,ExuA,RevEx,RevDiff,
' SettlingTime,
Integ
,Mult,Offset)
Resistance
(X,1,mV50,1,Ix1,1,2,True,True,0,250,1,0)
'Calculate RS and RS_RS0:
RS = ((-R2*R4) - (X*(R1+R2+R4))) / (X-R1)
RS_RS0 = RS/RS0
....'Calculate temperature from RS_RS0:
'PRTCalc(Dest,Reps,Source,PRTType,Mult,Offset)
PRTCalc
(DegC,1,RS_RS0,1,1.0,0)
NextScan
EndProg
Summary of Contents for CR3000 Micrologger
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Page 485: ...Section 8 Operation 485 8 11 2 Data Display FIGURE 110 Keyboard and Display Displaying Data ...
Page 487: ...Section 8 Operation 487 FIGURE 112 CR1000KD Real Time Custom ...
Page 491: ...Section 8 Operation 491 FIGURE 116 Keyboard and Display File Edit ...
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Page 564: ...Section 11 Glossary 564 FIGURE 126 Relationships of Accuracy Precision and Resolution ...
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