Maybe you could test the instrument protocol by connecting the instrument to a PC comm port. Run the Hyperterminal program and configure the COMM port as a direct connect at 2400/E/7/1. If the instrument is transmitting continuously you should see the text of the protocol flow on the Hyper Terminal screen.

If HyppppppppppprrrerTtterrrrrrminalllll gives you fits then consider downloading the very fine WINHEXCOM program from:
http://www.aerospacesoftware.com/winhexcom.html

Michael Karas