pH ARC Sensors Modbus RTU Programmer’s Manual (EPHUM011)
2.7.7 Currently active Calibration Parameters part 3
In register 5520, 5528 and 5560 the pH value of the used calibration standards, the electrical potential of the pH sensor and the temperature upon calibration are stored.
Start | Number | Reg1 / | Reg3 / | Reg5 / | Reg7 / | Modbus | Read | Write |
register | of | Reg2 | Reg4 | Reg6 | Reg8 | function | access | access |
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5520 | 8 | pH value of | Electrical | Electrical | free | 3, 4 | A/S | none |
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| calibration | potential at | potential at |
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| standard at | CP1 | CP1 |
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| CP1 [pH] | [mV] | [mV] |
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5528 | 8 | pH value of | Electrical | Electrical | free | 3, 4 | A/S | none |
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| calibration | potential at | potential at |
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| standard at | CP2 | CP2 |
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| CP2 [pH] | [mV] | [mV] |
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5560 | 8 | pH value of | Electrical | Electrical | free | 3, 4 | A/S | none |
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| product at | potential at | potential at |
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| CP6 [pH] | CP6 [mV] | CP6 [mV] |
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Figure 2.7.7.1: Definition of register 5520, 5528 and 5560.
Command: Act calibration CP1 | Modbus address: 5520 |
| Length: 8 | Type: 3 | Read | ||
Parameter: | pH CP1 [pH] | Voltage CP1 [mV] | Temp | CP1 [K] | free |
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Format: | Float | Float | Float |
| Float |
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Value: | 4.003401 | 179.927 | 297.1378 | 0 |
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Figure 2.7.7.2: | Example to read the | actual calibration values | of CP1. |
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Command: Act calibration CP2 | Modbus address: 5528 |
| Length: 8 | Type: 3 | Read | ||
Parameter: | pH CP2 [pH] | Voltage CP2 [mV] | Temp | CP2 [K] | free |
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Format: | Float | Float | Float |
| Float |
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Value: | 7.006804 | 3.099747 | 296.6901 | 0 |
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Figure 2.7.7.3: Example to read the actual calibration values of CP2.
Command: Act calibration CP6 | Modbus address: 5560 | Length: 8 | Type: 3 | Read | ||
Parameter: | pH CP6 [pH] | Voltage CP6 [mV] | Temp | CP6 [K] | free |
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Format: | Float | Float | Float |
| Float |
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Value: | 7.1 | 5.10469 | 298.3302 | 0 |
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Figure 2.7.7.4: Example to read the actual calibration values of CP6.
2.7.8 Currently active Calibration Parameters part 4
For standard calibration (CP1 / CP2) register 5448 documents offset at pH7 and slope:
Start | Number | Reg1 / Reg2 |
| Reg3 / Reg4 | Reg5 / Reg6 |
| Modbus | Read |
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register | of | (Float) |
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| function | access |
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5448 | 6 |
| Offset at |
| Slope (25 °C) | Reference |
| 3, 4 |
| U/A/S |
| none | |||
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| pH 7 [mV] |
| [mV/pH] | temperature [K] |
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Figure 2.7.8.1: Definition of register 5448. |
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Command: Calculated cali values |
| Modbus address: 5448 | Length: 6 |
| Type: 3 | Read |
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Parameter: | Offset at pH 7 | Slope |
| Ref temp |
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| [mV] |
| [mV/pH] |
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Format: |
| Float |
| Float |
| Float |
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Value: |
| 3.607782 |
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| 298.15 |
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Figure 2.7.8.2: Example to read register 5448: offset at pH 7 is 3.6 mV; slope is -59.5 mV/pH; reference temperature is 298.15 K (=25°C)
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