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pH ARC Sensors Modbus RTU Programmer’s Manual (EPHUM011)
624300/01 page 49 / 67
2.7.7 Currently active Calibration Parameters part 3
In register 5520, 5528 and 5560 the pH value of the used calibration standards, the electrical potential
of the pH sensor and 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 pH value of
calibration
standard at
CP1 [pH]
Electrical
potential at
CP1
[mV]
Electrical
potential at
CP1
[mV]
free 3, 4 A/S none
5528 8 pH value of
calibration
standard at
CP2 [pH]
Electrical
potential at
CP2
[mV]
Electrical
potential at
CP2
[mV]
free 3, 4 A/S none
5560 8 pH value 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 calibration CP1
Modbus address: 5520 Length: 8 Type: 3
Read
Parameter: pH CP1 [pH] Voltage CP1 [mV] Temp CP1 [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 calibration CP2
Modbus address: 5528 Length: 8 Type: 3
Read
Parameter: pH CP2 [pH] Voltage CP2 [mV] Temp CP2 [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 calibration CP6
Modbus address: 5560 Length: 8 Type: 3
Read
Parameter: pH CP6 [pH] Voltage CP6 [mV] Temp CP6 [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 standard calibration (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: Calculated cali values
Modbus address: 5448 Length: 6 Type: 3
Read
Parameter: Offset at pH 7
[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
temperature is 298.15 K (=25°C)