The Agilent Varian 525 Cold Cathode ionization gauge tube measures pressures down to 1 x 10^-7 torr with accuracy and reliability. Response time from full to half scale pressure is less than 1 second. The 525 cold cathode gauge is bakeable only to a maximum of 100 °C. When properly maintained, the 525 starts at very low pressures where ordinary cold cathode gauges are difficult to start. Excellent repeatability and improved stability are provided by the linear response below 1 x 10^-2 Torr.

The cold cathode tube will operate in any orientation. A user suppled RG-58 cable with BNC connector, up to 1000 ft. long, is used to supply high voltage. The tube generates a strong magnetic field, so the user needs to handle the tube with care around other magnetic material. The tube should be protected from direct exposure to mechanical and diffusion pump fluids. Rapid venting of the tube to atmosphere will not cause damage to the 525 gauge tube. Rapid contamination of the 525 cold cathode ion gauge tube will occur if it is operated at pressures above 10^-1 Torr for extended periods of time.