def displayExternal(internValue,decimals=4,dim='Length'):
    '''return an internal value (ie mm) Length or Angle converted for display according 
    to Units Schema in use.'''
    from FreeCAD import Units
    if dim == 'Length':
        qty = FreeCAD.Units.Quantity(1.0,FreeCAD.Units.Length)
        pref = qty.getUserPreferred()
        conversion = pref[1]
        uom = pref[2]
    elif dim == 'Angle':
        qty = FreeCAD.Units.Quantity(1.0,FreeCAD.Units.Angle)
        pref=qty.getUserPreferred()
        conversion = pref[1]
        uom = pref[2].decode('latin-1')
    else:
        conversion = 1.0
        uom = "??"
    fmt = "{0:."+ str(decimals) + "f} "+ uom
    displayExt = fmt.format(float(internValue) / float(conversion))
    return displayExt