pH ARC Sensors Modbus RTU Programmer’s Manual (EPHUM011)
2 pH ARC Sensor Commands in Modbus RTU
2.1General
In order to communicate with a pH ARC Sensor over Modbus RTU protocol a Modbus master terminal application software is needed. The Modbus RTU is an open standard and a number of free and commercial application toolkits are available.
This manual contains examples and illustrations from WinTECH Modbus Master ActiveX Control tool: WinTECH
In the present manual the addressing of the Modbus registers starts at 1. But the Modbus master protocol operates with register addresses starting at 0. Usually, the Modbus master software translates the addressing. Thus, the register address of 2090 will be translated by the Modbus master software to 2089 which is sent to the sensor (Modbus slave).
Attention:
When configuring and calibrating the sensor, please limit write operations to a reasonable number. More than 100’000 write operations will physically damage the memory of the sensor.
Furthermore, for the Free User Memory Space (see chapter 2.9.3), the write operations are limited to 10’000.
2.2Operator levels and Passwords
2.2.1 Reading / Setting Operator Level
A pH ARC Sensor can be operated in three different operator levels. Each operator level allows a defined access to a specific set of commands.
Abbreviation |
| Description |
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| Code (hex) | Password (decimal) |
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U |
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| User (lowest level) |
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| 0x03 | 0 |
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A |
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| Administrator |
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| 0x0C | 18111978 |
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S |
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| Specialist |
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| 0x30 | 16021966 |
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Figure 2.2.1.1: | Definition of operator level and default passwords |
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At each power up or processor reset, the operator level falls back to the default level U. |
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The active operator level can be read and written in register 4288. |
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Start |
| Number of | Reg1 / Reg2 |
| Reg3 / Reg4 |
| Modbus |
| Read | Write |
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register |
| registers |
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| function code |
| access | access |
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4288 |
| 4 |
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| Operator Level |
| Password |
| 3, 4, 16 |
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| U/A/S | U/A/S |
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Figure 2.2.1.2: Definition of register 4288. |
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Command: Active operator level |
| Modbus address: 4288 | Length: 4 |
| Type: 3 | Read |
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Parameter: |
| Operator level |
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| Password |
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Format: |
| hex |
| decimal |
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Value: |
| 0x03 |
| 0 |
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Figure 2.2.1.3: Example to read the active operator level (function code 3, start register address 4288, number of registers 4): The active operator level is 0x03 (User). The sensor does not report the password. The value 0 is returned instead.
624300/01 | page 5 / 67 |
