Campbell Scientific CR3000 Micrologger - Manual (Page 162)

Section 7. Installation
162
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 * (R
0
– R
1
) + K * (T
1
– T
0
) + (S
0
– S
1
)
where,
G = gage factor (0.036 PSI/digit is typical)
R
0
= output at the zero state (out of water)
R
1
= measurement
K = temperature correction coefficient (‐0.04 PSI / C° is typical)
T
0
= r temperature at the zero state
T
1
= temperature measurement
S
0
= barometric pressure at the zero state
S
1
= 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.