Dwyers: Flow meters

Kobold: Flow meters

McCrometer: Flow meters

Siemens: Flow meters

B/W Controls: Continuous level relays, 
relays, floats, control panels, and conductivity

Danfoss: Flow switches and sensors.

Dwyers: Switches and sensors.

Gems

Gems: Sensors, switches, and indicators.

Kobold: Switches and sensors.