Thermo Electron of Waltham, Mass., has increased...

Thermo Electron of Waltham, Mass., has increased its stake in Monitor Technologies of San Diego to 5.12%, according to a statement filed with the Securities and Exchange Commission.

Thermo Electron, a process equipment maker, said it bought 36,000 common shares of Monitor Technologies, a maker of automated gas analyzers, for investment between March 17 and May 2 for $2.75 a share. Thermo now holds 90,600 Monitor common shares.