Mediapost reports Nielsen is beginning to measure the Internet usage of national TV broadcasts.

The test is considered controversial in some research circles, because it is being conducted live on Nielsen’s national TV ratings sample, and theoretically could impact the stability of Nielsen’s core TV research. But Nielsen executives have maintained that the impact of measuring both TV and online behavior in a small subset of its sample households would be minimal, and that they would monitor the situation closely to ensure there is no impact on the quality of its national TV ratings.

Nielsen plans to begin measuring TV and Internet usage in 375 of its people meter sample homes before making a decision this fall to expand it. One concern is the reluctance some Nielsen families might have to sharing their online usage behavior with researchers.