Tektronix ( TEK) rose 33% early Monday after Danaher ( DHR) agreed to buy the electronic testing company for $38 a share, or $2.8 billion, in cash.

The deal offers shareholders of Beaverton, Ore.-based Tektronix a 34% premium to Friday's closing prices. Tektronix would become part of Danaher's Electronic Test platform, joining Danaher's Fluke and Fluke Networks businesses, and nearly doubling the platform's revenues.

Tektronix rose $9.16 to $37.50.