7. Sub-assemblies
The provisions for sub-assemblies may apply to sub-assemblies manufactured by the same or different manufacturers. Where a thermal energy meter consists of sub-assemblies, the essential requirements for the thermal energy meter apply to the sub-assemblies as relevant. In addition, the following apply:
7.1.The relative MPE of the flow sensor, expressed in %, for accuracy classes:
where the error Ef relates the indicated value to the true value of the relationship between flow sensor output signal and the mass or the volume.
7.2.The relative MPE of the temperature sensor pair, expressed in %:
where the error Et relates the indicated value to the true value of the relationship between temperature sensor pair output and temperature difference.
7.3.The relative MPE of the calculator, expressed in %:
where the error Ec relates the value of the thermal energy indicated to the true value of the thermal energy.
7.4.The critical change value for a sub-assembly of a thermal energy meter is equal to the respective absolute value of the MPE applicable to the sub-assembly (see points 7.1, 7.2 or 7.3).
7.5.Inscriptions on the sub-assemblies
| Flow sensor: | Accuracy class |
| Limits of flow rate | |
| Limits of temperature | |
| Nominal meter factor (e.g. litres/pulse) or corresponding output signal | |
| Indication of the direction of flow | |
| Temperature sensor pair: | Type identification (e.g. Pt 100) |
| Limits of temperature | |
| Limits of temperature difference | |
| Calculator: | Type of temperature sensors
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