Dear Nanda
Thank you for choosing National Instruments!
National Instruments provides drivers for NI products only. If you need drivers for other third party hardware, you will need to contact the hardware manufacturer for the drivers and VIs to interface with LabVIEW. You can go to the download center for Keithley from this
link and typing in DAS 1600 in the search page. This will bring up a section with downloads - wherein you can find driver updates. If you do not find information here, then you may need to call in tech support for Keithley to get the drivers.
Hope this helps.
Thanks and Regards
ShekharS
National Instruments