Thousand Oaks-based Teledyne Technologies has agreed to purchase a New York-based electronics testing instruments maker in a deal valued at $291 million.

Teledyne, an industrial-defense conglomerate, is set to purchase Chestnut Ridge-based LeCroy Corp. for $14.30 a share, for a total of about $240 million. Stock options, appreciation rights and net debt push the deal value to $291 million.

LeCroy has about 500 employees and marked $178.1 million in sales during its last fiscal year. Its flagship products are high-end oscilloscopes, which are instruments used to test and refine complex electronics.

Teledyne CEO Robert Mehrabian, a former dean of the UC Santa Barbara College of Engineering, said that by combining LeCroy’s instruments with new technologies developed at Teledyne Scientific Co., the firm could introduce a new range of equipment used in designing electronics. “LeCroy will broaden our portfolio of analytical instrumentation businesses by adding a leader in electronic test and measurement solutions,” Mehrabian said in a release. Teledyne shares were up about 1 percent to $60.40 on the news.

Teledyne is the third largest public company based in the Tri-Counties, with a market capitalization of $2.2 billion and $1.9 billion in revenue during 2011.