Campbell Scientific CS431 Submersible Pressure Transducer - Manual (Page 9)

CS431 Submersible Pressure Transducer
• Compute the normalized ratiometric output (L) as: L = (Vo/Vr) * 100.
• Apply calibration/scaling values (from INW calibration sheet) to convert
to psi: multiplier * L + offset.
To get the temperature measurement, the datalogger program should do the
following:
• Apply excitation voltage across T1 (orange) and AG (black).
• Measure voltage output across T2 (brown) and AG (black).
• Apply math to process and linearize the measurement, resulting in degrees
centigrade.
Two programming languages are used with our dataloggers, CRBasic and
Edlog. CRBasic is compatible with our CR800, CR850, CR1000, CR3000,
CR5000, and CR9000(X) dataloggers. Edlog is compatible with older
dataloggers such as our CR7, CR500, CR510, CR10(X), 21X, and CR23X.
Both CRBasic and Edlog are included in PC400, LoggerNet, and RTDAQ
Datalogger Support Software. Example CRBasic programs are provided in
Section 5.1.1. and example Edlog programs are provided in Section 5.2.1.
5.1 CRBasic Instructions
Apply 800 mV excitation voltage as follows:
ExciteV(Vx1,800,0)
Wait 25 milliseconds, as follows:
Delay(0,25,msec)
Use the VoltDiff( ) function to read Vr and Vo, as follows:
VoltDiff
(Vr,1,mV25,1,false,0,_60Hz,1.0,0)
VoltDiff (Vo,1,mV25,2,true,0,_60Hz,1.0,0)
The fifth parameter (RevDiff) is false when measuring Vr and
true when measuring Vo. When RevDiff is true a second
measurement is made with the inputs reversed, in order to help
compensate for offsets in the circuitry, thus giving a more
accurate reading. On a 9805, the Vr (excitation) cannot be
reversed, however, the Vo (output) can and should be to give the
best readings. NOTE
Compute the L factor (normalized ratiometric output) as follows:
L = 100 * (Vo/Vr)
Apply calibration values and convert to pressure in psi as follows:
P = m * L + b
Where m and b are obtained from the calibration sheet supplied by INW.
For even more accurate readings, advanced calibration values can be applied.
(See Section 5.1.1.2.)
Temperature is read using the Therm107 instruction, as follows:
Therm107
(Temp,1,5,Vx3,0,_60hz,1.0,0)
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