Here the pressure is measured through a gas discharge within a gauge head
whereby the gas discharge is ignited by applying a high tension. The resulting ion
current is output as a signal which is proportional to the prevailing pressure. The
gas discharge is maintained also at low pressures with the aid of a magnet. New
concepts for the design of such sensors permit safe and reliable operation of
these socalled Penning sensors in the pressure range from 10-2 to 1 x 10-9
mbar/Torr.