The system will give broadcasters a better idea of what impact VOD, which allows viewers to watch shows when they feel like rather than when they are listed, is having on traditional television viewing habits.
Nielsen will also measure on-demand viewing of older programmes and movies from the libraries of content providers.
The media research firm will use the same electronic survey it uses for traditional ratings when it launches its VOD service next month.
According to Reuters, the system could give a boost to the future of advertising support for VOD, by providing a basis for the buying and selling of commercial time within VOD content.
However, the new service will not measure on-demand viewing of TV programmes shown over the internet or downloaded to PCs.
Nielsen, a unit of media and market research company VNU, has been measuring TV audiences since the 1949-50 broadcast season.
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