Ron Nersesian, who heads Agilent Technologies' Sonoma County division, was promoted Thursday to the No. 2 spot at the $6.6 billion high-tech manufacturer.

Nersesian, 52, was named chief operating officer at Agilent, giving him day-to-day responsibility for its three business units: chemical analysis, life sciences and the Santa Rosa-based Electronic Measurement Group.

"Ron has done a superb job of leading Agilent's electronic measurement business," Agilent president and CEO Bill Sullivan said in a statement. "He was responsible for a complete transformation of EMG, resulting in outstanding profitable growth in current as well as emerging markets."

Santa Clara-based Agilent reported its best year in history on Tuesday. Much of its growth is being driven by demand for next-generation smartphones.

To replace Nersesian, Agilent tapped Guy S??to lead the electronic measurement division. S?? 56, has been vice president of the company's microwave and communications business since 2009.

Nersesian joined Hewlett-Packard in 1984 two years after graduating from Lehigh University and went to Agilent when it was spun off from H-P in 1999. He held various management posts over the last three decades, coming to Santa Rosa in 2005 as vice president of its wireless unit.

Nersesian said Thursday he'll continue to live in Santa Rosa, splitting his time between Sonoma County, Santa Clara and customer locations around the world.

Agilent's Santa Rosa campus is headquarters and research-and-development center for the measurement group. It has about 1,150 employees.

"Santa Rosa will continue to be a very strong part of Agilent," Nersesian said.

S??was his choice to head the measurement group. "He's a very strong leader with great people skills and business skills," Nersesian said.

Nersesian took over the electronic measurement group — Agilent's largest business — in 2009, when the tech company was feeling the impact of the economic downturn.

Agilent lost $31 million that year as hard-pressed consumers stopped buying the latest electronic gadgets.

The measurement group laid off 3,000 of its 11,000 employees around the world, including 300 in Santa Rosa.

But business started to bounce back in 2010, especially in Asia, where most electronics are manufactured. Demand for Agilent's test instruments is surging as device makers roll out new wireless technology.

Agilent delivered the best operating performance in its history during the fiscal year ended Oct. 31, Sullivan told Wall Street analysts Tuesday.

The measurement group reported a record 24 percent operating margin on fourth-quarter sales of $855 million.

Agilent hasn't hired back many of the measurement employees laid off in 2009, a move that lowered its costs and has boosted profit margins.