Not all devices support the Model drop-down menu. Complete the following tasks if the device you want to change doesn't have a Model drop-down menu:
Delete the device model you no longer want to use and add the desired device model from the palette.
(VISA) If the VISA device is not matched to a device in the Live view, type the device you want into either the Vendor or Model field. If your VISA device is matched to a device in the Live view, you must disable hardware matching before you can replace the device on the Design view. On the document toolbar, click to stop matching devices between the SystemDesigner views.