Easy Chart - Calculated Pen to multiply two pens

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Is there a way to create a calculated pen to multiply two different pens? I see sum and difference options, but the only multiplication I can find is to multiply a pen by a scalar.

If not, is there any neat workaround? I could create a new tag in our directory that is simply the product of the two tags in question, but the unfortunate drawback of that solution is that I lose out on tag history.

Thanks!

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There is no way to do this from the easy chart.

You do have options though:

Assuming that you can't just do the math in the device and create an OPC Tag with the history enabled.

  1. Switch from using an Easy Chart and use the Standard Chart component. You have to do a little more work, but it is completely capable of doing anything that the Easy chart can do.
  2. Create an expression tag that multiplies the two tags together and set it's history to also be recorded. (Technically this is also possible with a Derived Tag, however, not exactly the use case you're needing)
  3. (If you have the SQL Bridge Module) Use a Transaction group to record the values into the a database, and an expression item to multiply the two tags in question together. Then on the Easy chart use Database Pens to display the data.
  4. Create a memory tag, and use a Gateway Tag Change event that is triggered off of a change in either of the factor tags, do the multiplication and write the value to the memory tag. Set the memory tags history to be recorded.
  5. Use Gateway Tag Change Events in combination with the system.tag.storeTagHistory() function to store the data to the tag historian including your own value that is the product of the two tags.

There may be other options that I can't think of at the moment, but as you can see you are far from blocked at accomplishing this.

I've listed these in the order of my preference. Arguably, my first approach is a little involved and not nearly as simple as some solutions, however, I much prefer the Standard Chart component to the Easy chart as it is not nearly as limited in it's functionality.

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