How to sample multiple channels with an Allen-Bradley CompactLogix PLC

For PLCs with fixed addressing like the Allen-Bradley MicroLogix Series, data must be stored in consecutive registers in order to sample multiple data points and store the data in a single datalog file so that multiple channels can be displayed in a Trend Display or History Data Display.

For tag-based PLCs like the CompactLogix, create an array and store the data in consecutive elements in the array (INT, DINT, or REAL array). Assign the Read address of the Data Sampling object to the first element in the array that contains the data to be sampled.

If this isn’t possible, or if the data being sampled has mixed data types, you can use the Global Data Transfer (Time-based) in EBPro to move the data from the PLC to consecutive LW (Local Word) addresses in the HMI, then assign the Read address of the Data Sampling object to the first LW register that contains the data to be sampled.

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