It could definitely be a problem with the EOS. Have you looked to see if the instrument uses a termination character, and if so which one? You may need to append this to the "*IDN?" string in order for the instrument to process the incoming command correctly. Your instrument will also need to be compliant with the SCPI standard (Standard Commands for Programmable Instruments) in order to respond to such commands as *IDN?, *TST?, and other standardized commands. This is probably not an issue, however, because most instruments produced today use SCPI.
I would also like to make you both aware that there are instrument drivers available for using these two instruments with LabVIEW. You can search for them from our instrument driver network, linked below. These drivers will make using the basic aspects of the instruments in LabVIEW much more simply.
National Instruments Instrument Driver NetworkHave a great day.
John M
Applications Engineer