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graphlabview

How to set two identical y-scales in the same graph in Labview?

When a graph is very wide I want to show the y-axis values also on the right side of the graph so it becomes easier to read the corresponding values of the lines.

I know how to duplicate the left axis to the right. And when the graph is created I use ActYscl to set the range of scale nr 0 (left) to scale nr 1 (right). This works when the graph is created and also the zoom and pan function work on both y-scales. However, when I use the Autoscale function of the Graph Pallet, only the initial axis is scaled (probably because the graph data are only linked to the original axis).

Is there a way to make the autoscale function work for both y-axis at the same time?

Solution

  • Charts and graphs have an Autoscale Range Change event. Use an event structure to catch this event and update the range of the duplicate scale to match the first one:

    chart on front panel

    VI snippet (drag on to your VI diagram)

    I've used a chart for this example as it's simpler, but it should work the same for a graph. Of course you need a way of telling the event loop when to exit; I've used the Value Changed event of the stop button. If your application uses an event-driven structure anyway, you should just be able to add the autoscale event to your existing event loop.