Main Page | See live article | Alphabetical index The portable people meter or PPM is a device developed by Arbitron to measure how many people are listening to the radio, and to which stations their radios are tuned. The device picks up the intermediate frequency produced by a radio when it demodulatess a station's signal, and the PPM logs each time it finds such a signal. It has proved to be much more accurate than the old handwritten logs, immune to forgetful test subjects, totally passive, and completely anonymous. It will soon be used to trigger changeable billboards to move to an advertisement most likely to influence the people currently looking at it, by matching that ad's target demographic with the people most likely to be listening to the station the PPM finds to be most popular at any given time. This article is from Wikipedia. All text is available under the terms of the GNU Free Documentation License.