Trying to calibrate an OBS-3+ turbidity probe. Using the code shown at the bottom from shortcut. However I constantly get negative values of around -198 which fluctuate by 2 or 3. It calcuates TurbNTU via a polynomial curve:
NTUS = A(X)2 + B(X) + C
Which looks like this in the code:
NTUArray(Count)=0.20709+(0.40111*NTUArray(Count))+(0.00003531*NTUArray(Count)^2)
No clue where to go from here. My Voltse reading seems to be staying at 0 as well which seems odd.
'CR800 Series 'Created by Short Cut (4.4) 'Declare Variables and Units Dim Count Public BattV Public PTemp_C Public TurbNTU Public NTUArray(21) Public VoltSE Units BattV=Volts Units PTemp_C=Deg C Units TurbNTU=NTU Units VoltSE=mV 'Define Data Tables DataTable(Table2,True,-1) DataInterval(0,1440,Min,10) Minimum(1,BattV,FP2,False,False) EndTable 'Main Program BeginProg 'Main Scan Scan(5,Sec,1,0) 'Default CR800 Datalogger Battery Voltage measurement 'BattV' Battery(BattV) 'Default CR800 Datalogger Wiring Panel Temperature measurement 'PTemp_C' PanelTemp(PTemp_C,_60Hz) 'OBS-3+/OBS300 Turbidity Sensor measurement 'TurbNTU' PortSet(9,1) Delay(0,2,Sec) For Count = 1 To 21 VoltSE(NTUArray(Count),1,mV2500,1,1,0,_60Hz,1,0) NTUArray(Count)=0.20709+(0.40111*NTUArray(Count))+(0.00003531*NTUArray(Count)^2) Delay(0,45,mSec) Next SortSpa(NTUArray(),21,NTUArray()) TurbNTU=NTUArray(11) If TurbNTU<250 Then For Count = 1 To 21 VoltSE(NTUArray(Count),1,mV2500,2,1,0,_60Hz,1,0) NTUArray(Count)=0.29928+(0.10569*NTUArray(Count))+(0.00000024763*NTUArray(Count)^2) Delay(0,45,mSec) Next SortSpa(NTUArray(),21,NTUArray()) TurbNTU=NTUArray(11) EndIf PortSet(9,0) 'Call Data Tables and Store Data CallTable Table2 NextScan EndProg