Section 7. Installation
342
PT100 BrFull() Four-Wire Full-Bridge Measurement
'This program example demonstrates the measurement of a 100-ohm PRT (PT100) in a four-wire
'full bridge with voltage 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
X1
'Raw output from bridge
Public
X2
'Calculated intermediate value
Public
RS
'Calculated PT100 resistance
Public
RS_RS0
'Calculated ratio RS/RS0
Public
DegC
'Calculated temperature of PT100
BeginProg
Scan
(1,Sec,0,0)
'Measure X
'BrFull(Dest,Reps,Range,DiffChan,ExChan,MeasPEx,ExmV,RevEx,RevDiff,SettlingTime,
'
fN1
(p. 584),
Mult,Offset)
BrFull
(X1,1,mV200,U1,U11,1,2500,True,True,0,15000,1,0)
'Calculate X2
X2 = (X1/1000) + (R2/(R1+R2)
'Calculate RS and RS_RS0
RS = (R4*X2) / (1-X2)
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
Notes
The following relationships are used in, or are related to, the previous procedure.
Maximum Excitation Voltage
Used:
V1
@maxT
= maximum voltage in the CR6 analog voltage input range
VX
MAX
= V1
@maxT
/((R3
@maxT
/(R3
@maxT
+R4)) – (R2/(R1+R2)))
Related:
V1
@maxT
= VX*((R3
@maxT
/(R3
@maxT
+R4)) – (R2/(R1+R2)))
Summary of Contents for CR6 Series
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Page 76: ...Section 5 Overview 76 FIGURE 20 Half Bridge Wiring Example Wind Vane Potentiometer ...
Page 80: ...Section 5 Overview 80 FIGURE 23 Pulse Input Wiring Example Anemometer ...
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Page 454: ...Section 8 Operation 454 FIGURE 104 Narrow Sweep High Noise ...
Page 459: ...Section 8 Operation 459 FIGURE 106 Vibrating Wire Sensor Calibration Report ...
Page 535: ...Section 8 Operation 535 8 11 2 Data Display FIGURE 121 CR1000KD Displaying Data ...
Page 537: ...Section 8 Operation 537 FIGURE 123 CR1000KD Real Time Custom ...
Page 538: ...Section 8 Operation 538 8 11 2 3 Final Storage Data FIGURE 124 CR1000KD Final Storage Data ...
Page 539: ...Section 8 Operation 539 8 11 3 Run Stop Program FIGURE 125 CR1000KD Run Stop Program ...
Page 541: ...Section 8 Operation 541 FIGURE 127 CR1000KD File Edit ...
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Page 610: ...Section 11 Glossary 610 FIGURE 137 Relationships of Accuracy Precision and Resolution ...
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