Campbell CR3000 Micrologger, Руководство оператора

Страница: 290 / 644

Section 7. Installation
290
Calibrate PRT
Used:
X
CAL
= (1000*(V1
CAL
/VX)), where (1000*(V1
CAL
/VX)) is the output of
BrFull() with Mult
= 1,
Offset
= 0
X3
CAL
= (X
CAL
*0.001) + (R2/(R1+R2))
Related:
V1
CAL
= VX*((R3
CAL
/(R3
CAL
+R4)) – (R2/(R1+R2)))
Slope, Offset, and Xp
M = 0.001
B = (R2/(R1+R2))
Xp = ((1000*(V1/VX))*M+B
Rs/R0, K, and temperature
Rs/R0 =
–(R4/((R4*X3
CAL
)/(1–X3
CAL
)))*(Xp/(Xp – 1))
K = (Rs/R0)
–1
T = (SQRT(d * (R/R0) + e)
– a) / f (see PRT Calculation Standards for
coefficients)
or
T = g * K^4 + h * K^3 + I * K^2 + j * K (see PRT Calculation Standards for
coefficients)
Resistance of the PRT (R3):
R3 =
(R4 • X3)/(1 – X3)
X3 = (X / 1000) + (R2/(R1
+ R2))
Measurement resolution:
There is a change of approximately 4 mV from the output at 40 °C to the
output at 51 °C, or 400 µV / °C. With a resolution of 0.33 µV on the ±50
mV range, this means that the temperature resolution is 0.0009 °C.
7.7.17.6
Example: 100 Ω PRT in Four
-Wire Basic Circuit (PT100 / Basic
Resistance() )
This example shows the simplest PRT setup and how to measure multiple PRTs
from one U terminal set up for current excitationIX terminal.