What are the differences between subject power sensors, if any? As I understand, Agilent took over HP's power sensor department (or the other way around?). My problem is there is a testing program we use that calls for an HP, but if you use and Agilent it will fail power measurement tests.
Agilent is basically the Test & Measurement Group that was formerly part of HP (and have to note we were the original piece of HP - before they ever made a computer or printer :-) ).
The transition to Agilent company name occurred in 2000. Products designed <2000 were simply rebranded, like the 8481D.
There are occasional design changes to a product, but if a major specification changes then they will change the model number (e.g. 8481D could become an 8481Z).
My recommendation is to do a performance test to confirm both 8481Ds meet specification (manual at http://cp.literature.agilent.com/litweb/pdf/08481-90173.pdf).
Hope this helps,
Mike