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Gamble

Displaying Data in a Line Graph

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What I would like to do is display some data recorded by a PLC as a line graph on an HMI. I was planning on using some type of PanelView, but as I looked into how the trend object works I think I may have to go with something else. The main problem is that the trend object (and line graph on an EZPanel) are all made to display data in real time and record it. What I would like to do is take a previously recored data set and display it on demand on an HMI. My data set tracks two variables each with 230 data points over about 0.5s of time. There will be up to 15 sets of this data stored at one time, and it needs to be able to be recalled and displayed on demand by the operator. One possible solution to this is to "feed" the requested data to the HMI whenever it is requested. There by simulating data in real time. The problems with this however is the timing between update/refresh rates, the PLC logic to "feed" the data, and trying to keep it from taking 20 seconds to draw a graph. I have run some simulations trying to do this, and I get poor graphs with missing data points. I hope I was clear in explaining my situation. Any suggestions?

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Some HMI's are capable of "backfilling" their trend data (I believe Citect is capable, ClearSCADA is another that can backfill but i think it is protocol dependant ie DNP3 is capable but I don't know about others) try checking with supplier of the particular HMI that you intend to use. What you are describibng is something that is reasonable popular amongst RTU's where the data is stored locally and retrieved infrequently. Yo may need to get creatinve in the search terms you are usning. Maybe there is a way in Panelview that you can put your data into it's (panelviews) trend file via a backdoor

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Anything that calls itself a "historian" and any HMI worth the disk it was installed from should easily support your requirement. You're right, devices like panelviews often just read the values as "realtime" and cache them in memory for a short term chart. It sounds like you want a system that records the values in a database. You have a lot of options here. I'm preferential to FactoryPMI, particularly if you plan on viewing the data from multiple stations. The graphing/charting engine is very powerful and it can deal with a lot of data stored in a standard SQL database. I'd contact Red Lion if you want a single terminal hardware (Panelview-like) solution. They appear to have more modern embedded software and seem to be popular on the forums. I wouldn't try to McGyver it as you mention in your last paragraph. You're mentioning a common problem that has been solved by nearly every vendor. Your decision should come down to additional project requirements.

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