Method 2
This method uses the following equations to calculate the temperature of the RTD. These equations more
accurately describe the relationship between temperature and impedance of the RTD than Method 1.
For Tc > 0 deg C (R(t)>100)
R(t) = R
0
(1 + A* Tc + B * Tc
2
)
For Tc < 0 deg C (R(t)<100)
R(t) = R
0
(1 + A*Tc + B * Tc
2
+ C (Tc-100)*Tc
3
)
Where R(t) = Resistance of RTD
R
0
= 100
Ω
A = 3.9083 * 10
-3
* deg C
-1
B = -5.775 * 10
-7
* deg C
-2
C = -4.183 * 10
-12
* deg C
-4
Below is an example program for using Method 2 that could run on the RIO-4712x.
Note:
The coefficients have been modified to avoid round off errors in the calculations in the temperature
readings.
#MAIN
REM set Analog inputs 0-5 to 0-5V inputs
AQ 0,3
AQ 1,3
AQ 2,3
AQ 3,3
AQ 4,3
AQ 5,3
AT0;'set initial time reference
#Calc
REM calculate resistance of RTD
r0 = (1000*@AN[0])/21
r1 = (1000*@AN[1])/21
r2 = (1000*@AN[2])/21
r3 = (1000*@AN[3])/21
r4 = (1000*@AN[4])/21
r5 = (1000*@AN[5])/21
REM calculate deg C
r=r0;JS#Celcius;Tc0 = Tc
r=r1;JS#Celcius;Tc1 = Tc
r=r2;JS#Celcius;Tc2 = Tc
r=r3;JS#Celcius;Tc3 = Tc
r=r4;JS#Celcius;Tc4 = Tc
r=r5;JS#Celcius;Tc5 = Tc
AT-100;'wait 100 ms from last time ref
JP#Calc
#Celcius
sqrt=@SQR[992137.445376*(761.2471-r)]
Tc = (-25613.43488+sqrt)/(-7.569408)
REM adjust for Tc < 0 deg C
IF (Tc < 0)
Ta=-(((Tc-100)*Tc*Tc)/239062873.536)*Tc
Ta = Ta * 0.2311
Tc = Tc - Ta
ENDIF
EN
96 A1 – SCB-48206
RIO-47xxx
Содержание RIO-47**0
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Страница 93: ...RIO Dimensions RIO 471xx Units in centimeters RIO 47xxx Appendix 87...
Страница 94: ...RIO 472xx Units in millimeters 88 Appendix RIO 47xxx...
Страница 107: ...Internal 56 64 Zero Stack 53 RIO 47xxx Index 101...