Campbell Scientific CR1000 Measurement and Control System - Manual (Page 259)

Section 7. Installation
259
0.15°C over the -10 to 40°C temperature range. Because the measurement is
ratiometric (R
S
/R
f
), the properties of the 10-kΩ resistor do not affect the result.
A terminal-input module (TIM) can be used to complete the circuit shown in
figure PT100 in Four-Wire Half-Bridge
(p. 259).
Refer to the appendix Signal
Conditioners
(p. 561)
for information concerning available TIM modules.
Figure 79: PT100 in four-wire half-bridge
CRBasic EXAMPLE. PT100 in Four-Wire Half-Bridge
CRBasic Example 59. PT100 in Four‐Wire Half‐Bridge
'See FIGURE. PT100 in Four-Wire Half-Bridge (p. 259) for wiring diagram
Public Rs_Ro
Public Deg_C
BeginProg
Scan (1,Sec,0,0)
'BrHalf4W(Dest,Reps,Range1,Range2,DiffChan1,ExChan,MPS,Ex_mV,RevEx,RevDiff,
' Settling, Integration,Mult,Offset)
BrHalf4W (Rs_Ro,1,mV25,mV25,1,Vx1,1,2200,True,True,0,250,1.0111,0)
'PRTCalc(Destination,Reps,Source,PRTType,Mult,Offset)
PRTCalc (Deg_C,1,Rs_Ro,1,1.0,0) 'PRTType sets alpha
NextScan
EndProg
7.8.18.2.3 PT100 in Three-Wire Half-Bridge
Example shows:
• How to measure a PRT in a three-wire half-bridge configuration.
Advantages:
• Uses half as many input channels as four-wire half-bridge.
Disadvantages:
• May not be as accurate as four-wire half-bridge.