RMS high frequency signal conditioner/transducer

Does anyone know of a vendor that sells high frequency voltage signal conditioners? My particular application has an approximately 500kHz 0-5VAC signal that I would like conditioned to give its RMS value as a DC voltage or a 4-20 mA signal. Ideal solution would be a BNC input device that is DIN mount, but this is not required. Has anyone come across anything like this? All conditioners I have found are relatively low frequency bandwith (most are <20kHz, one I found was 100kHz). The basic arrangement in my application is plant -> probe -> (conditioner) -> data logger.

Thanks,

I didn’t find the right solution from the internet.

References:

http://www.engineering.com/AskForum/aft/1783.aspx

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