Can we have 3 different PI tags which reads data from single Instrument tag?
This depends on the interface as well as a number of other factors. For example, with the PI OPC DA Interface it disallows having multiple tags with the same instrument tag, but you would be pulling in the same data twice. Whereas for the RDBMS interface, the instrument tag might be identical across multiple tags because it's a reference to a specific SQL file and then the Extended Descriptor is used to differentiate the data being pulled in by the tags.
Can I ask you what interface you're using to pull this data? Additionally, what's you're end goal in this process? I ask this because oftentimes when a technical question like this is asked, it's usually being though of as the only way to accomplish something when in fact there might be an easier/different/preferred method.
A clarification on the last statement made, PI Interface for OPC DA does allow for multiple PI Tags to have the same Instrument Tag.
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