Hi Ronald,
I assume you have Fp-1001 network module since you are using a RS-232-485 converter. The update rate of FP-AI-100 is 360 S/s (2.8ms) which is fast enough for the update rate you mentioned. If your application requires faster update rate, you might also consider the data throughput rate. Here's the link to the Knowledgebase that explains it in detail.
http://digital.ni.com/public.nsf/3efedde4322fef19862567740067f3cc/0d418c9097f14e99862567c300666568?OpenDocument
Regards,
Remzi A.