Campbell Scientific CR800 and CR850 Measurement and Control Systems - Manual (Page 159)

Section 7. Installation
159
Public Offset(3)
Alias Offset(1) = Digits_Offset
Alias Offset(2) = Temp_Offset
Alias Offset(3) = BP_Offset
Public LoadResult, CalMode
Public AVWRC
Const GageFactor = 0.01664
Const Temp_K = -0.00517
BeginProg
'Load the calibration constants stored in the CAL file after a zero is performed
LoadResult = LoadFieldCal(False)
Scan (1,Sec,1,0)
'AVW200(AVWRC,Com1,0,200,VW(1,1),1,1,1,1000,4000,1,_60Hz,1,0) '<
'instruction (commented out)
'Digits_Measured=(VW(1,1)^2)/1000 '<
Digits_Measured = 8746
'Temp_Measured=1/(1.4051E-3 + 2.369E-4 * LN(VW(1,6))+1.019E-7 * LN(VW(1,6)) ^3)-273.15
Temp_Measured = 21.4
'VoltSE(BP_Measured,1,mV2500,5,1,0,_60Hz,0.2,600) '<
'(commented out)
BP_Measured = 991
FieldCal (4,Equation_Parameters(),3,0,Offset(),CalMode,0,1,1)
Pressure = (GageFactor * (Digits_Measured - Digits_Offset) + Temp_K * _
(Temp_Measured - Temp_Offset) - (BP_Measured - BP_Offset) * 0.014503)
NextScan
EndProg
7.8.1.5.4 Two-Point Slope and Offset (Option 2)
Case: A meter measures the volume of water flowing through a pipe. Multiplier
and offset are known to drift, so a two-point calibration is required periodically at
known flow rates. The following procedure adjusts multiplier and offset to correct
for meter drift as shown in the calibration report below. Note that the flow meter
outputs milliVolts inversely proportional to flow.
Table 24. Calibration Report for Flow Meter
Parameter Parameter at Deployment Parameter at 7 Day Service
SignalmV output @ 30 L/s 300 mV 285 mV
SignalmV output @ 10 L/s 550 mV 522 mV
Multiplier -0.0799 L/s/mV -0.0841 L/s/mV
Offset 53.90 L 53.92 L