Campbell Scientific CS547A-L Conductivity/Temperature Probe and A547A Interface - Manual (Page 19)

CS547A Conductivity and Temperature Probe and A547 Interface
The calibration solution temperature must be between 1°C and 35°C; a
polynomial is used to correct for temperature errors within this range. The
solution constant of 1.408 mS cm
-1 (for prepared solution mentioned above), is
valid only for a 0.01 molal KCl solution.
6.4.1 CRBasic Calibration Program Example
'CR1000 Datalogger
'Field Calibration program to determine new Cell Constant (Kc) for CS547A conductivity probe
Public Rs, Rp, T
Dim T_25, f_of_T
Public Conductivity, Kc
Const CalSolution = 1.408
'for 0.01 molal KCL solution
'Data Table not required for Field Calibration – monitor “Kc” in Public table
'Main Program
BeginProg
'edit cable length (Rp) to reflect footage of actual lead length
Rp = 25 'feet
Scan (10,Sec,0,0)
BrHalf(Rs, 1, mV2500, 2, VX1, 1, 2500, True, 0, 250, 1, 0)
Rs =(Rs/(1-Rs))
'correct for resistance of cabling
Rs = Rs + (((Rp*.00032)* -0.1) - 0.005)
'compensate for temperature effects
Therm107 (T,1,3,Vx2,0,_60Hz,1.0,0)
T_25 = (T-25) * 0.01
f_of_T = 0.99124 - (1.8817*T_25) + (3.4789*T_25^2) - (3.51*T_25^3) - (1.2*T_25^4)
- (43*T_25^5)
Conductivity = (1/f_of_T)*CalSolution
Kc = Conductivity * Rs
NextScan
EndProg
6.4.2 Edlog Calibration Program Example
In step 11, the polynomial instruction (P58) is used to correct for temperature
errors within the 1°C to 35°C range. In step 13, the solution constant of
1.408 mS cm
-1 is entered by using P37. Location 8 [Kc(cm -1 )], generated by
Step 14 will contain the resultant cell constant.
1: AC Half Bridge (P5)
1: 1
Rep
2: 15 2500 mV fast Range (5000 mV fast for 21X)
3: 2 IN Chan
4: 1 Excite all reps w/EXchan 1
5: 2500 mV Excitation (5000 mV for 21X)
6: 1 Loc [Rs ]
7: 1 Mult
8: 0 Offset
13