Campbell Scientific CR3000 Micrologger - Manual (Page 164)

Section 7. Installation
164
'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 26. 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
1. Send the program in CRBasic example FieldCal Multiplier and Offset
Demonstration Program
(p. 165)
to the CR3000.
2. To simulate the flow sensor, place a jumper wire between channels VX1 and
SE6 (3L).
3. Simulate deployment-calibration conditions (output @ 30 l/s = 300 mV, output
@ 10 l/s = 550 mV) in two stages.
a. Set variable SignalmV to 300. Set variable KnownFlow to 30.0.
b. Start the deployment calibration by setting variable CalMode = 1.
c. When CalMode increments to 3, set variable SignalmV to 550. Set
variable KnownFlow to 10.
d. Resume the deployment calibration by setting variable CalMode = 4