Bad Quality Alarm for Device Disconnected

How is the Bad Quality alarm configured? I assume it is configured to look at the tags quality to see if it is Bad. I tried to set this alarm up to notify when a device becomes disconnected but it did not work. The value of the tag for the disconnected device read Error_TypeConversion and when I bound it to a label it read NaN in red. I am not 100% sure but I think the Quality value on the tag was Good when the device became disconnected. What is the Quality looking at if what I said it true? I did try a different time to disconnect a device. Are there any other ways I can try to set this up?