Understanding the historian on a driven tag


I am using Ignition Vision 8.1 and am looking for a way to only save periodic tag data to the historian only when a condition is met. Please let me know if I am doing this correctly:

  1. Setup a tag group, “Machine1_Running” with a driven mode and a driving expression to validate the condition, i.e. “{[default]Machine/1/LineSpeed}>0” .

  2. The tag to be recorded, “Machine1_ProcessTempPV” would get assigned to the tag group “Machine1_Running”. History would get be enabled, storage provider selected and sample mode set to periodic 1 second (in this case I need periodic, not on change).

By setting up the tag this way, is it correct to assume that the tag will only update when the machine is running and that also the historian will also only save data when the machine is running?

Is there a way to set up the tag so that it continuously shows the actual value but only logs to the historian when a condition is met? This way, the current value could show on a dashboard, but wouldn’t unnecessarily consume historian space.

Thank you