How to change units when Measuring with DWG FastView

Some users want to change units when they measuring with DWG FastView, but DWG FastView only display results when measuring, no units. 

When the drawing you want to open is with the Metric System, the result you measured with DWG FastView will be displayed in metric (no unit displayed). 

If the drawing you open is with the British System, you can set the scale by yourself, and the measurement result can also be displayed in metric.

For example:

A drawing with the British System, a line 500 inches(but inches is not displayed).

I want this line show in metric(m)

I need to set scale '1:0.0254'  ( 1 inch= 0.0254m)

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So the result show in metric!