Ask Farmer: How long until sensors are used to track first downs and TDs?

Have a question about the NFL? Ask Times NFL writer Sam Farmer, and he will answer as many as he can online and in the Sunday editions of the newspaper throughout the season. Email questions to: sam.farmer@latimes.com.

What’s the status of sensors in the ball and sidelines to get rid of first-down chains, and determine if the ball crossed into end zone?

Greg Kimbrough, Riverside

Farmer: NFL spokesman Brian McCarthy says the league has been testing a variety of those devices for a number of years. “We will continue testing and evaluation, but nothing is imminent,” he said.

Several companies have worked on the chip-in-ball technology. About five years ago, a team of engineering students at Carnegie Mellon University developed a “smart football” with a miniature GPS unit and accelerometer contained in a half-ounce microchip inside the ball. The chip measured factors such as ball speed, spin, trajectory, and the precise location of the football even when it’s buried under a pile of players.

German manufacturer Cairos Technologies has been in talks with the NFL about putting similar chips in balls. The company has done so with soccer balls, creating a system of thin cables under the playing surface that generate magnetic fields that are picked up by sensors in the ball. That location information is transmitted to a central computer, which uses the data to determine when the ball has crossed the goal line. When a goal has been scored, the computer alerts the referee by transmitting a radio signal to his watch. There are unique challenges to embedding a similar chip in an oblong football.

“You can’t change the weight, the spiral, the torque or the feel of the football,” Priya Narasimhan, then an associate professor at Carnegie Mellon University, told The Times in 2011. “It is really critically important, otherwise you’ve just ruined the whole purpose.”

What’s the longest drive in NFL history? It has to be over 100 yards. For example, if the team started on their own one-yard line and eventually scored, the drive would be 99 yards. But if they were penalized 15 yards along the way, the drive would be 114 yards.

Ray Uhler, Rancho Santa Margarita

Farmer: Because drives aren’t measured that way, the NFL doesn’t keep those statistics, nor does the Elias Sports Bureau, which seems to tabulate everything under the sun.

However, the league is using player-tracking technology called Next Gen Stats to answer questions such as: How many miles per hour is a player running? How open was that receiver? How many extra yards did that running back travel in his serpentine path to the end zone? This season, every pair of NFL shoulder pads will be fitted with two radio-frequency chips that are roughly similar to a GPS device and allow the league to track player’s movements.