pH ARC SensorsModbus RTU Programmer’s Manual (EPHUM011)
624300/01 page 49/ 67
2.7.7 Currently active Calibration Parameters part 3
In register 5520, 5528and 5560 the pH value of the used calibration standards, the electrical potential
of the pH sensorand the temperature upon calibration are stored.
Start
register Number
of
registers
Reg1 /
Reg2 Reg3/
Reg4 Reg5/
Reg6 Reg7/
Reg8 Modbus
function
code
Read
access Write
access
5520 8 pHv alue of
calibration
standardat
CP1 [pH]
Electrical
potential at
CP1
[mV]
Electrical
potential at
CP1
[mV]
free 3, 4 A/S none
5528 8 pHv alue of
calibration
standardat
CP2 [pH]
Electrical
potential at
CP2
[mV]
Electrical
potential at
CP2
[mV]
free 3, 4 A/S none
5560 8 pHv alue of
product at
CP6 [pH]
Electrical
potential at
CP6 [mV]
Electrical
potential at
CP6 [mV]
free 3, 4 A/S none
Figure 2.7.7.1:Definition of register 5520, 5528 and 5560.
Command: Act calibrationCP1 Modbusaddress: 5520 Length: 8Type: 3Read
Parameter: pH CP1 [pH] Voltage CP1 [mV] TempCP1 [K] free
Format: Float Float Float Float
Value: 4.003401 179.927 297.1378 0
Figure 2.7.7.2:Example to read the actual calibration values of CP1.
Command: Act calibrationCP2 Modbusaddress: 5528 Length: 8Type: 3Read
Parameter: pH CP2 [pH] Voltage CP2 [mV] TempCP2 [K] free
Format: Float Float Float Float
Value: 7.006804 3.099747 296.6901 0
Figure 2.7.7.3:Example to read the actual calibration values of CP2.
Command: Act calibrationCP6 Modbusaddress: 5560 Length: 8Type: 3Read
Parameter: pH CP6 [pH] Voltage CP6 [mV] TempCP6 [K] free
Format: Float Float Float Float
Value: 7.1 5.10469 298.3302 0
Figure 2.7.7.4:Example to read the actual calibration values of CP6.
2.7.8 Currently active Calibration Parameters part 4
For standardcalibration (CP1 / CP2) register 5448 documents offset at pH7 and slope:
Start
register Number
of
registers
Reg1 / Reg2
(Float) Reg3/ Reg4
(Float) Reg5/ Reg6
(Float) Modbus
function
code
Read
access Write
access
5448 6 Offset at
pH 7 [mV] Slope (25 °C)
[mV/pH] Reference
temperature [K] 3, 4 U/A/S none
Figure 2.7.8.1: Definition of register 5448.
Command: Calculatedcali values Modbusaddress: 5448 Length: 6Type: 3Read
Parameter: Offset at pH7
[mV] Slope
[mV/pH] Ref temp
[K]
Format: Float Float Float
Value: 3.607782 -59.47631 298.15
Figure 2.7.8.2: Example to read register 5448: offset at pH 7 is 3.6 mV; slope is -59.5 mV/ pH; reference
temperatureis 298.15K (=25°C)