LOS ANGELES -- In a world with hundreds of television channels, figuring out who's watching what is about to get easier.
For decades, viewing habits have been tracked through devices attached to TVs and radios in the sample. Thousands of households also kept paper diaries during the crucial television "sweeps" periods in February, May, July and November.
That low-tech system is getting a major upgrade.
The two major companies that produce television and radio ratings are testing next-generation technology that would give advertisers the data they need to decide where to spend their billions of dollars.
The most promising is the "portable people meter," a beeper-like device being developed by Arbitron, which logs programming seen or heard anytime, anywhere by whomever is wearing it.
People need to do nothing more than wear it during the day and place it in a home docking station each night so data can be transmitted to Arbitron.
The device uses sensitive microphones to pick up codes embedded in television, radio and even streaming Internet broadcasts - and it includes a motion detector to verify someone is actually wearing it.
"With the portable people meter, we know that you carried it and what it was exposed to," said Thom Mocarsky, a spokesman for Arbitron, which compiles radio ratings.
With diaries, he said, Arbitron has to guess whether a blank diary page means "they didn't listen to radio or forgot to log in."
Arbitron just completed the first phase of testing, strapping meters on 1,500 testers in Philadelphia. The results were more comprehensive than data collected by current means - in large part because viewing and listening outside the home was included.
There was also more information on viewing and listening by young males - a key demographic group for advertisers - who are notoriously sloppy about recording their habits in diaries, Mocarsky said.
Nielsen Media, which provides television ratings, is watching the tests closely, with an eye toward forming a joint venture with Arbitron to roll out the technology nationally.
Nielsen is testing its own meter to monitor similar embedded codes. Unlike the Arbitron device, the Nielsen meter attaches to individual television sets.
Both systems could become essential as digital television eventually replaces the analog technology now in use.
"Digital changes the way television is transmitted, so the channel-based measuring system goes away," said Nielsen spokesman Jack Loftus. "Everyone is going to encoding, and the race is on to see whose code is better."
Advertisers are carefully monitoring both prototypes in their search for more accurate ratings data.
"The (paper) diary is incapable of picking up detailed cable information," said Susan Nathan, senior vice president and director of media knowledge at Universal McCann, part of the Worldwide McCann advertising agency. "We know the diary is inferior. We have lived with it forever, and it's time to get off it."
The constant tracking afforded by personal people meters, Arbitron believes, will eventually eliminate the need for sweeps weeks, when quality programming is often bunched together on the same nights to the frustration of viewers.
Currently, national and local television ratings are measured by Nielsen Media Research using electronic devices supplemented four times a year by paper diaries.
Nationally, 5,000 randomly selected homes are equipped with a meter on each television in the house to log which channels are watched. A second measurement is made by assigning each household member a separate button on the device, which is turned on and off when the person starts and stops watching television.
Detailed demographic statistics for various age groups are gleaned from the data.
Radio ratings are collected entirely using paper diaries.
The new personal people meters, which likely won't be used nationally for three to five years, also promise a solution to the thorny issue of tracking how people use personal video recorders to time-shift TV programs and zap advertising. It will reveal if a person is watching live or taped shows and can detect gaps that indicate fast-forwarding through ads.
Advertisers are excited about the reams of new data and say they can't wait for the technology to be perfected.
"Advertisers are on the air 365 days a year, 24 hours a day," Nathan said. "To not be accountable to them for the majority of that in 2002 is just ridiculous."