Chromatography Forum

Im planning in purchasing a ionization gauge for our HP5890/5972 MSD system.

I noticed that there are two versions of the gauge. One version has only the 'gauge' button while another has both 'gauge' and 'degas' button. Im not sure what's the difference or if I need both options.

The Degas option uses another filament in the gauge tube to heat the tube up to help drive off gasses trapped in the filaments or the glass. It won't activate until your analyzer pressure is below 5x10^-5torr. I think they removed the option later on because too many people would leave the degas on for too long and the heating filament would sag and short out the tube.

Either will work, except if the tube doesn't have the degas filament it won't do anything when you turn it on, but both will read the vacuum.

Hi James,

Thanks for the input.

We just received our ionization gauge (2 button version). I tested it out and it displays 9.9+9 on the screen but then turns off (ie. LCD) after about 20 sec. Is this normal?

Please note the unit was not under vacuum or even connected to the GC, I simply placed on the table and turned it on.

Im not sure if the unit needs to be under vacuum for it to work properly. Hoping it's not defective.

Yes it needs to be under vacuum. It should shut down to protect the filaments if not under enough vacuum. It usually needs to be in the 10^-3 torr range before it will stay on.

Thanks James! I was worried for a bit, I'll test it out under vaccum,