The Agilent durable and rebuildable 525 cold cathode ionization gauge tube measures pressures from 1 x 10^-8 to 1 x 10^-2 Torr (1 x 10^-8 to 1 x 10^-2 mbar) and has excellent repeatability, accuracy, and reliability. Sudden exposures to atmospheric pressure will not cause any damage.

Similar in configuration to the inverted magnetron gauge, the 525 starts at very low pressures where ordinary cold cathode gauges are difficult to start.