Hi NJG88:
This is a VISA serial error, so I'm assuming you are communicating through a serial port, as opposed to GPIB. If so this typically occurs when the baud rate is not set correctly in the program. Are you using LabVIEW? If so please be sure that you set the baud rate to the correct value in the VISA Configure Serial Port VI.
Thank you,
Emilie S.
Applications Engineer
National Instruments