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7.2.1 CS240 programming
The CS240 program needs to measure the resistance of the CS240 then convert that resistance
measurement to temperature.
7.2.1.1 Resistance measurement
CRBasic instructions used to measure resistance are the
(2-wire configuration). The
BrHalf
instruction uses the fewest input terminals.
BrHalf()
A typical
BrHalf4W()
BrHalf4W(CS240X,1,mV200,mV200,U1,U5,1,350,True,True,0,60,1,0)
A typical
BrHalf()
BrHalf(CS240X,1,mV200,U7,U3,1,350,True,0,60,1,0)
Use a multiplier of 1.0 and offset of 0.0 in the instructions.
7.2.1.2 Converting resistance measurement to temperature
The
instruction converts the ratio Rs/Ro to temperature, where Rs is the measured
PRTCalc()
resistance of the RTD, and Ro is the resistance of the RTD at 0 degrees Celsius (1000 Ω).
A typical
PRTCalc()
PRTCalc(PRTtemp,1,Rs/1000,1,1,0)
If the
instruction (2-wire configuration) was used to measure resistance, the following
BrHalf()
expression also must precede the
Rs=CS240X*(1000+R
Where CS240X value returned by the
provided on the cable label.
7.2.2 CS240DM programming
NOTE:
Programming basics for the CR6 and CR1000X data loggers are provided in this section.
Contact Campbell Scientific if using a data logger that requires an MD485 interface.
CS240 and CS240DM PT-1000 Class A, Back-of-Module Temperature
BrHalf4W()
instruction is:
instruction is:
instruction is:
PRTCalc()
)/(1–CS240X)–R
c
c
BrHalf()
(4-wire configuration) or
BrHalf4W
instruction reduces cable errors, and the
instruction:
instruction and R
is the cable resistance
c
Sensors 12
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