5 pt100s with current excitation, Figure 83: pt100 in four-wire full-bridge, Crbasic example 61. pt100 in four-wire full-bridge – Campbell Scientific CR3000 Micrologger User Manual

Page 268

Section 7. Installation

268

Figure 83: PT100 in four-wire full-bridge

CRBasic Example 61. PT100 in Four‐Wire Full‐Bridge

'See FIGURE. PT100 in Four-Wire Full-Bridge

(p. 268)

for wiring diagram.

Public

BrFullOut

Public

Rs_Ro

Public

Deg_C

BeginProg

Scan

(1,Sec,0,0)

'BrFull(Dst,Reps,Range,DfChan,Vx1,MPS,Ex,RevEx,RevDf,Settle,Integ,Mult,Offset)

BrFull

(BrFullOut,1,mV50,1,Vx1,1,5000,True,True,0,250,.001,.02344)

'BrTrans = Rf*(X/(1-X))

Rs_Ro = 50 * (BrFullOut/(1 - BrFullOut))

'PRTCalc(Destination,Reps,Source,PRTType,Mult,Offset)

PRTCalc

(Deg_C,1,Rs_Ro,2,1.0,0)

NextScan

EndProg

7.8.18.2.5 PT100s with Current Excitation

Example Shows:

• How to measure multiple PRTs with current excitation.

Advantages:

• Higher accuracy. Common excitation errors for all sensors in a series, which

results in smaller differential errors.

• Uses only one differential channel per PRT.

Disadvantages:

• If one series connection breaks, all sensors in the series will fail.