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pH ARC Sensors Modbus RTU Programmer’s Manual (EPHUM011)
624300/01 page 50 / 67
2.7.9 Special Commands for Calibration with VISICAL
The VISICAL calibration device allows calibration of pH ARC Sensors at CP1 or CP2. The pH ARC
Sensor’s associated calibration parameters for CP1 and CP2 are those predefined and stored in
corresponding registers of the sensor.
Register 5164 defines the pH value for CP1 and register 5196 defines the pH value for CP2, which are
only valid for use with VISICAL. The same calibration limits for the pH value are used as for standard
calibration at CP1 and CP2 (register 5152 and 5184 respectively).
Attention:
It is not possible to perform a product calibration using VISICAL.
Physical unit is fixed to pH by definition.
Start
register
Number of
registers
Reg1 / Reg2 Modbus
function code
Read
access
Write
access
5180 2 pH value at CP1 (default: pH 4.00) 3, 4, 16 U/A/S S
5212 2 pH value at CP2 (default: pH 7.00) 3, 4, 16 U/A/S S
Figure 2.7.9.1: Definition of register 5180 for CP1 and 5212 for CP2.
Command: VISICAL CP1
Modbus address: 5180 Length: 2 Type: 3
Read
Parameter: Value [pH]
Format: Float
Value:
4.00
Figure 2.7.9.2: Example to read the pH value valid for CP1. It is 4.00. Accordingly, the next time when a
calibration is started using VISICAL at LOW, a calibration with manual selection is performed,
using the calibration standard at pH 4. The operator has to make sure that - within the selected
set of calibration standards - a standard at pH 4 is selected for manual selection.
Command: VISICAL CP2
Modbus address: 5212 Length: 2 Type: 16
Write
Parameter: Value [pH]
Format: Float
Value:
7.00
Figure 2.7.9.3: Example to set the pH value valid for CP2.
Command: VISICAL CP2
Modbus address: 5212 Length: 2 Type: 3
Read
Parameter: Value [pH]
Format: Float
Value:
7.00
Figure 2.7.9.4: Example to read the pH value valid for CP2. It is 7.00. Accordingly, the next time when a
calibration is started using VISICAL at HIGH, a calibration with manual selection is performed,
using the calibration standard at pH 7. The operator has to make sure that - within the selected
set of calibration standards - a standard at pH 7 is selected for manual selection.