Campbell Scientific CR3000 CR3000 Micrologger - Page 162

Section 7. Installation BeginProg Multiplier = .05 Offset = 0 LoadFieldCal(true) 'Load the CAL File, if possible Scan(100,mSec,0,0) 'Simulate measurement by exciting channel VX1/EX1 ExciteV(Vx1,mV,0) 'Make the calibrated measurement VoltSE(SaltContent,1,mV5000,6,1,0,250,Multiplier,Offset) 'Perform a calibration if CalMode = 1 FieldCal(1,SaltContent,1,Multiplier,Offset,CalMode,KnownSalt,1,30) 'If there was a calibration, store it into a data table CallTable(CalHist) NextScan EndProg 7.8.1.5.3 Zero Basis (Option 4) Case: A non-vented piezometer (water depth pressure transducer) needs its offset zeroed before deployment. Because piezometer temperature and barometric pressure have strong influences on the pressure measurement, their offsets need to be zeroed as well. The relationship between absolute pressure, gage pressure, and piezometer temperature is summarized in the linear equation, pressure = G * (R0 - R1) + K * (T1 - T0) + (S0 - S1) where, G = gage factor (0.036 PSI/digit is typical) R0 = output at the zero state (out of water) R1 = measurement K = temperature correction coefficient (‐0.04 PSI / C° is typical) T0 = r temperature at the zero state T1 = temperature measurement S0 = barometric pressure at the zero state S1 = barometric pressure measurement. The following procedure determines zero offset of the pressure transducer, water temperature, and barometric pressure readings. Use the integrated keyboard / display or support software numeric monitor to change variable values as directed. 162