The name Keller has earned its place in the History of Pressure Measurement, as it is closely connected with the development of the piezoresistive technology. Silicon die on gold header In the 60`s, company founder H. W. Keller developed the first integrated silicon pressure measuring cell at the Honeywell Research Center in Minneapolis. He also patented the integrated production method of this silicon cell in the United States.Keller pressure and level measurement products. From OEM pressure sensors to sophisticated autonomous water level loggers, most can be found here Products of National Semiconductor, Foxboro, and Honeywell have been directly or indirectly developed on the basis of this work.