pH ARC Sensors Modbus RTU Programmer’s Manual (EPHUM011)
2.4.5 Configuration of the 4-20 mA Interface
Note:
The configuration of AO1 / AO2 is only effective if register 4360 / 4488 (active analog interface mode) is set to the value 0x01, 0x02 or 0x04.
2.4.5.1Reading the Available Primary Measurement Channels to be Mapped to the Analog Output
Start | Number of | Reg1 / Reg2 | Modbus | Read | Write |
register | registers |
| function code | access | access |
4362 | 2 | Available Primary Measurement Channels | 3, 4 | U/A/S | none |
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| for AO1 |
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4490 | 2 | Available Primary Measurement Channels | 3, 4 | U/A/S | none |
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| for AO2 |
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Figure 2.4.5.1.1: Definition of register 4362 / 4490.
For the definition of the Primary Measurement Channels (PMC), see chapter 2.5.
Primary Measurement Channel (PMC)
PMC1 (pH)
not available
0x20 PMC6 (temperature)
Figure 2.4.5.1.2: Code for selection of the primary measurement channel.
Command: Available PMC AO1 | Modbus address: 4362 | Length: 2 | Type: 3 | Read | |||
Parameter: | Available PMC 20 mA |
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Format: | hex |
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Value: | 0x21 |
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Figure 2.4.5.1.3: Example to read the available Primary Measurement Channels (PMC) for AO1. The hexadecimal value of “0x21”defines that PMC1 (pH) or PMC6 (temperature) can be mapped to AO1. Register 4490 contains the same value “0x21”. Accordingly, PMC1 or PMC6 can be mapped to AO2 as well.
2.4.5.2Selecting the Primary Measurement Channel to be Mapped to the Analog Interface
Start | Number of | Reg1 / Reg2 | Modbus | Read | Write |
register | registers |
| function code | access | access |
4364 | 2 | Selected PMC for AO1 | 3, 4, 16 | U/A/S | S |
4492 | 2 | Selected PMC for AO2 | 3, 4, 16 | U/A/S | S |
Figure 2.4.5.2.1: Definition of register 4364 / 4492. Only one bit can be set.
Command: Active PMC AO1 | Modbus address: 4364 | Length: 2 | Type: 3 | Read | |||
Parameter: | Current PMC 20mA |
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Format: | hex |
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Value: | 0x01 |
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Figure 2.4.5.2.2: Example to read the current primary measurement channel mapped to AO1, defined in register 4364. The value “0x01”is returned, saying that PMC1 is mapped to AO1 (factory setting).
The factory setting for register 4492 is “0x20”, mapping PMC6 to AO2.
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