pH ARC SensorsModbus RTU Programmer’s Manual (EPHUM011)
624300/01 page 33/ 67
2.7.2 Definitions of Calibration Points
2.7.2.1 Calibration Points 1 and 2 (Standard Calibration)
The limitsf or thecalibration point 1 are defined in register 5152, for calibration point 2 in register5184.
Start
register Number of
registers Reg1/ Reg2 Reg3 / Reg4 Reg5 / Reg6 Modbus
function code Read
access Write
access
5152 6 Physical unit
currently
activef or
CP1
Min value for
CP1 (in the
physical unit
as defined in
Reg1 and2)
Max value for
CP1 (in the
physical unit
as defined in
Reg1 and2)
3, 4 U/A/S none
5184 6 Physical unit
currently
activef or
CP2
Min value for
CP2 (in the
physical unit
as defined in
Reg1 and2)
Max value for
CP2 (in the
physical unit
as defined in
Reg1 and2)
3, 4 U/A/S none
Figure 2.7.2.1.1: Definition of register 5152 for CP1 and 5184 for CP2.
Attention:
The only physicalunit available for calibration is pH ! The physical unit defined in 5152, 5184 and 5312
for CP1, CP2 andCP6 is NOT linked to the physical unit defined for PMC1 in register 2090.
When performinga calibration while having the physical unit set to “mV”, the calibrationstatus will
report “CP1:incorrect measurement unit”or “CP2:incorrect measurement unit”(seef igure 2.7.4.1.1).
Command: Calibrationlimits CP1 Modbus address: 5152 Length: 6Type: 3Read
Parameter: Unit Min value Max value
Format: Hex Float Float
Value: 0x01000 0 0
Figure 2.7.2.1.2: Exampleto readthe limits of CP1. Currently active physical unit is pH (0x01000). The
min and maxv aluesare both 0, indicating, that calibration at CP1 can be performed only using
defined calibrationstandards having discrete pH values.
Command: Calibrationlimits CP2 Modbus address: 5184 Length: 6Type: 3Read
Parameter: Unit Min value Max value
Format: Hex Float Float
Value: 0x01000 0 0
Figure 2.7.2.1.3: Examplet o read the limits of CP2. The active physical unit is is pH (0x01000). The
min and maxv aluesare both 0, indicating, that calibration at CP2 can be performed only using
defined calibrationstandards having discrete pH values.
When initiatingthe calibration at CP1 and CP2, the measured pH and temperature have to be stablef or
at least 3 minutes.The stability criteria are defined in register 5128:
Start
register Number of
registers Reg1/ Reg2
(Float) Reg3/ Reg4
(Float) Modbus
function code Read
access Write
access
5128 4 Max. Drift PMC1
pH
[pH/min]
Max. Drift PMC6
Temperature
[K/min]
3, 4, 16 U/A/S S
Figure 2.7.2.1.4:Definition of register 5128.