RSLinx OPC to OSI PI - Reading Data Options

civicseth

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Join Date
May 2014
Location
Ledbetter
Posts
9
Currently, we are using RSLinx OEM for an OPC server and connecting to an L35 CompactLogix. I am reading correct data for some tags in the processor, but had a question on a better way to gather this data.

We have boxes pass over a weigh scale and that weight is stored in a register and is used to determine whether the box meets specified weight to determine if it is "kicked out" or send to palletized. I am pulling this weight into our PI historian, but the way the data is logged it is a "real" value. So when I pull up PI data in Excel and specify a scan time interval, PI will extrapolate between actual weight readings.

I want to be able to use PI to determine when a box is weighed and what batch number it is. I can currently see the batch number, but the data is stored the same way as the weight. PI extrapolates between actual readings, so I do not know the exact moment a box is scanned, whether the weight represents the actual weight, or if that is extrapolated data. Is there a way to push the data, per say, one time when the registers that hold the weight and batch number changes, along with a time stamp? Currently, there is no way to know the exact moment the weight register changes, etc.

I hope this was clear enough, but I can clarify anything if need be.

We want to be able to see what a box weighs, it's batch number only when one is passed over the scale. PI is treating the registers(data) in the same way as a pressure (constantly changing), but this data needs to be treated almost like discrete data...a particular weight, or no weight.
 
Almost three years later, and we are revisiting this after abandoning for a while.

I'm now wanting to store a box weight from the scale, scanned bar code weight, and the batch number (all of these are in registers in the PLC already) into a buffer array...along with the time stamp the box passes a certain photo eye. I have been looking into doing a FIFO instruction to get these multiple data points into a multi-variable array, and set a bit once these are full, so PI will see the change and pull this data in.

I'm having a hard time finding much information on getting these registers moved into an array with the time stamp.
 
I believe you are using an available but unsuitable tool to record and store production data.

PI Historians are process databases and are intended to be used for engineering purposes; yes, you could 'implement' some sort of production data recording, however, it will still be a surrogate.

Case in point, add six more INTs to the production data array and write within the PLC_Year, PLC_Month, PLC_Day, PLC_Hour, PLC_Minutes and PLC_Seconds respectively; the six tags will be the first six elements of a INT[7] Data Type (PLC_DateTime) where a GSV instruction will extract the Controller's DateTime Attribute. If you Production Data array is of a DINT Data Type you will have to BTD(Bit Distribute) the six INTs within three DINTs.

Or, and this would be my approach, use a production data designated Relational Historian (SQL Type database) such as Ignition or Wonderware Historian and record any Data Type data aggregated within any Data Type, user defined 'containers' (columns). One SQL record could contain SINTs, INTs, DINTs, LINTs, REALs, STRINGs, DATETIMEs, etc. all recorded with a single 'trigger', neatly stored and easily/readily available for further reference.
 

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