Campbell CR3000 Micrologger, Руководство оператора

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Section 7. Installation
288
c. Measure with BrFull(). If you are doing a dry run, assume the result of
Resistance()
= X
10
= 0.7491.
d. Calculate RS
10
:
X2
10
= (X
10
/ 1000) + (R2 / (R1 + R2) = 0.02036
RS
10
= (R4 • X2
10
) / (1 – X2
10
) = 103900
6. Calculate RS
10
/RS
0
, K, and temperature:
a. RS
10
/RS
0
= 1.039
b. K = (RS
10
/RS
0
)-
1 = 0.039
c. T = g * K^4 + h * K^3 + i * K^2 + j * K = 9.99 °C
d. T = (SQRT(d * (RS
10
/RS
0
) + e) -
a) / f = 9.99 °C
1
A Campbell Scientific terminal-input module (TIM) can be used to complete the resistive bridge
circuit. Refer to the appendix Passive-Signal Conditioners — List
(p. 605).
4
Get this value from a PRT-resistance-to-temperature table
CRBasic Programs and Notes
PT100 BrFull() Four-Wire Full-Bridge Calibration
'This program example demonstrates the calibration 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
Public X1 'Raw output from the bridge
Public X2 'Calculated intermediate value
Public RS0 'Calculated PT100 resistance at 0 °C
BeginProg
Scan (1,Sec,0,0)
'Measure X1
'BrFull(Dest,Reps,Range,DiffChan,ExChan,MeasPEx,ExmV,RevEx,RevDiff,SettlingTime,
'
Integ ,Mult,Offset)
BrFull (X1,1,mV50,1,Vx1,1,5000,True,True,0,250,1,0)
'Calculate X2:
X2 = (X1/1000) + (R2/(R1+R2)
'Calculate RS0:
RS0 = (R4*X2) / (1-X2)
NextScan
EndProg