IONIVAC-Transmitters ITR are active sensors (pressure to voltage converters) which are based on the Bayard-Alpert principle. A hot cathode emits electrons which impinge on an anode. The gas of which is to be measured, is thus ionized. The resulting positive ion current is detected through the third electrode and this current is used as the signal which is proportional to the pressure. The Hot Cathode Ionization sensors offer a wide measurement range of 10^-10 to 10^-1 mbar (0.75·10^-10 to 0.75·10^-1 Torr).