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pH ARC Sensors Modbus RTU Programmer’s Manual (EPHUM011)
624300/01 page 18 / 67
2.5 Measurement
2.5.1 Definition of Measurement Channels and Physical Units
The pH ARC Sensor Modbus register structure allows the definition of 6 individual Primary
Measurement Channels (PMC), and 16 individual Secondary Measurement Channels (SMC).
Bit # Hex code Description Definition
0 (LSB) 0x000001 PMC1 pH
1 0x000002 PMC2 not available
not available
4 0x000010 PMC5 not available
5 0x000020 PMC6 Temperature
6 0x000040 SMC1 R glass
7 0x000080 SMC2 R reference
8 0x000100 SMC3 R auxiliary
9 0x000200 SMC4 E pH vs. ref
10 0x000400 SMC5 E SG vs. ref
11 0x000800 SMC6 E aux vs. ref
12 0x001000 SMC7 E reference
13 0x002000 SMC8 pH act
14 0x004000 SMC9 T act
15 0x008000 SMC10 not available
…
21 (MSB) 0x200000 SMC16 not available
Figure 2.5.1.1: full list of PMC1 to 6 and SMC1 to 16.
In Register 2048, the available PMC and SMC are defined for a specific pH ARC Sensors and a
specific operator level.
Start
register
Number of
registers
Reg1 / Reg2 Modbus
function code
Read
access
Write
access
2048 2 Available measurement channels
PMC and SMC (bitwise set)
3, 4 U/A/S none
Figure 2.5.1.2: Definition of register 2048.
Command: Avail. PMC and SMC
Modbus address: 2048 Length: 2 Type: 3
Read
Parameter: Avail. PMC and
SMC
Format: Hex
Value: 0x06E1
Figure 2.5.1.3: Example to read Reg. 2048 for Polilyte Plus ARC.
In case of operator A/U, the value 0x06E1 is returned. In other words the following PMC and
SMC are available to A/U: PMC1 / PMC6 / SMC1 / SMC2 / SMC4 / SMC5
In case of operator S, the value 0x066E1 is returned. In other words the following PMC and SMC
are available to S: PMC1 / PMC6 / SMC1 / SMC2 / SMC4 / SMC5 / SMC8 / SMC9